Eccles set up FanDuel with husband Nigel, but she left the firm two years ago. She is now behind Relish, the “first-ever truly customised relationship training app” – offering users unlimited access to a qualified relationship coach combined with an “actionable, interactive and scientifically-backed” training plan.
It debuted in the US last week, has thousands of paying subscribers already, and will launch in the UK by the end of the year, Eccles told Scotland on Sunday.
The New York-based businesswoman saw a gap in the market to harness technology to bring people together, and Relish has a key presence in Edinburgh focused on the technical side, where it has seven staff and plans to increase this.
It also has a team of three in New York, taking care of the likes of marketing and coaching, while the firm also has a handful of part-time staff. Relish has been backed by $2.2 million (£1.8m) in funding from Trinity Ventures and Bullpen Capital, which invested in Edinburgh-founded FanDuel.
Eccles said the app is well-suited to couples seeking to tackle problems in what can be a more economical and convenient manner than seeing a relationship counsellor.
A total of 16 per cent of users have been together for less than two years, and 10 per cent for more than 20. "There’s a wide variety of people that are using it, but the main thing is that they’re looking for is to feel more connected," Eccles said.
She also said the launch comes amid growing customer willingness to pay for quality content.
"We’re ambitious and excited about the growth that we’ve seen already [with Relish] and just keen to keep it going," she added. "If I can make a difference to even a few people’s lives I’ve done what I set out to do. I feel really passionate about the mission."
As for whether it can be as big as New York-based FanDuel, which reached "unicorn" status with a $1 billion valuation and merged with Paddy Power Betfair's US business, there’s “no reason why it can’t be... in terms of ambition and growth, I’m not out to build a small business".
She added: "We have lots of plans. There are lots of ways we can expand this."
The launch comes hot on the heels of the publication of Billion Dollar Fantasy, focusing on online fantasy sports and looking at FanDuel and DraftKings - with the rights having been bought by TriStar Pictures.
FanDuel’s co-founders have quibbled over what they were owed after the company’s $465m acquisition.
Lesley Eccles said she had originally not wanted to get involved in another start-up after FanDuel, but was tempted back and started mulling ideas. "I was determined that whatever it was would be as impactful as FanDuel was - but much more mission-driven," she says.