Here are the niche-st dating apps on the market

The number of dating apps and online services has ballooned in recent years, serving increasingly niche markets. CNBC examines some of the most unusual products available.

— By Luke Graham, News Assistant

HerSmile is an online dating site and app launching on International Women's Day, which aims to make sure users' intentions are sincere.

Female users pay a monthly subscription of £12 ($17), while men buy introductory credits. Men have to spend one of their credits to send their first message to a woman, and if she's not interested then the credit is returned. The site claims this will prevent women from being bombarded with messages, as men have to commit their credits only to people they're genuinely interested in.

"By protecting women online and ensuring men aren't misled we can considerably reduce the time taken for both sexes to meet a genuinely suitable partner," explained Cosmo Currey, the site's founder, in a press release.

Dead Meet is a dating and networking site for people in the death industry, such as pathologists, funeral directors, taxidermists and anatomists.

"Dead Meet is about a year-and-a-half old. It's free and slowly building thanks to lots of press," said Carla Valentine, who runs the site, to CNBC in an email.

"The members are all over the world but at the moment our Dead Meet-ups are only in London," she said. "It has over 1,000 members worldwide and I've started a new 'member of the month' feature to showcase everyone's unique talents."

Credit: Lozzy Bones

Happn gets rid of the matching algorithms used by most dating apps and instead matches users based on if they've crossed paths in real life.

Since launching in February 2014, the app has attracted around 10 million users and is growing at a rate of 1.5 million new users a month. It has a target of 30 million users by the end of 2016.

"The people that users see on the timeline are the people they cross paths with, the people who are just around themselves and the fact that you live in the same area or you work in the same area means also that you have a lot of things in common," Happn's CEO Didier Rappaport told CNBC in an interview.

According to Rappaport, the demand for dating apps like Happn is only set to grow.

"We are talking about an essential need, which is the one of meeting other ones," he said. "This is a need which is urgent today because we can see in all the big cities that despite the density of the people, the people they really have difficulty to meet each other."

If you don't have the time or energy to find someone on a dating app, ODately will do the work for you. The concierge service, which only launched in February, guarantees clients two dates per month for £250 ($353), four dates for £400 and six dates for £500; it claims to have a growing waiting list of clients.

"It's a premium service, built for cash-rich but time-poor individuals living in major cities, who want to outsource their online dating," the company's founder Jack Kenyon told CNBC via email.

After an in-depth consultation, where ODately discusses the client's personal background, the company chooses an appropriate dating site or app, sets up a profile and speaks to potential dates on their client's behalf.

U.K. adult retailer Ann Summers launched its own dating app, Rabbit, earlier this year.

According to Jacqueline Gold, CEO of Ann Summers and Knickerbox, the app is growing daily, and has seen nearly 18,000 matches.

Some of its features include brand partnerships, allowing users to book and arrange date venues within the app. It also focuses on safety by never storing or showing a user's location to others.

"Online safety is of real importance so we also prevent users from sending inappropriate pictures which we learnt from our focus groups is one of the biggest frustrations women have with other dating apps," Gold told CNBC via email.

Spoonr is for those who just need a hug. The app finds prospective cuddlers close to the user's current location and users send cuddle requests to others to start chats. Users can then share their location and the app will provide walking directions to meet.

Spoonr has more than 300,000 users and claims to be the biggest social network for cuddlers, according to a spokesperson for the app.

TinderUs is a consultancy firm that develops the profiles of Tinder app users. It suggests the best photos for clients to use, improves their profile tagline and opening lines and also gives advice on flirting.

TinderUs charges clients $50 and has had over 200 bookings, according to its founder Michael Raven.

"Our consultants are early-20s women, who work in fashion, who give guys a second opinion on their profiles, what images they think would best portrait themselves, and how they should present themselves online," he told CNBC via email. "These simple methods really do improve a profile - it's all about getting a second opinion."

U.S. meat company Oscar Mayer launched its own dating app for bacon lovers in September last year. The app matched users based on multiple factors, including how crispy they liked their bacon and whether they preferred pork or turkey.

Oscar Mayer discontinued the app in February this year, but said during its lifetime the app had 25,000 users and made 50,000 matches.

PlayDate connects dog owners to set up playdates for their pets (and to meet their owner) in the local area. It was launched in Israel seven months ago and currently has 4,000 active users, according to founder Gary Feuerstein.

"Playdate is indeed a social dating app in the way that we use the dog as a common ground for people to meet," he told CNBC in an email. "The app is location based and allows you to swipe through other dog owners in your area. If you find a cute dog (or that pretty blond that walks her dog in your street every morning) you can engage by sending him/her a playdate invitation to walk the dog together."

Feuerstein does have plans to launch the app abroad.

"The app is completely free and we intend to start monetizing by selling pet related services and products at a later stage," he added. "We are currently in the process of raising capital for an international expansion."

The dating app Once ignores the conventions of most dating apps. It uses human matchmakers to pair users… and only gives users one match a day.

"You receive one match per day at noon, which is selected firstly by an algorithm filtering a list of matches based upon your age, location etc. Then a human matchmaker will decide from this list who they believe you are best suited with," explained Jean Meyer, the founder of Once, in a press release.

Once also has a heartbeat feature. It interacts with smartwatches like Fitbit to monitor the heart's reaction when the user sees the daily match and uses the data to improve future matches.

The app, which was announced in January, has 1 million users worldwide, according to the company.