A mobile app born in Birmingham is promising a quiet payment and customer loyalty revolution after completing its national launch.

Droplet, the brainchild of tech entrepreneurs Steffan Aquarone and Will Grant, has used £575,000 of crowd-funding cash raised via Crowdcube to take the fee-free payment app into seven new cities across the UK.

More than 300 independent retailers across Cambridge, Edinburgh, Exeter, Glasgow, Leeds, Manchester and Norwich are now accepting transactions via the app.

The pair came up with the idea in 2011 while sitting in independent Birmingham café Urban Coffee Company.

Mr Aquarone said: "There seems be a real appetite among consumers to buy from independent retailers and support community shopping and we're trying to tap into this with the national rollout.

"What originally started as a way of making payments over your phone has evolved a fair bit and we have coincided the national launch with the introduction of Droplet Rewards, which is basically a loyalty platform for local merchants.

"This means they can provide digital stamps to their customers in return for special offers and free treats like a cup of coffee or glass of wine.

"They can also message the local Droplet community via the app. In essence, we are offering a rewards scheme that can match a lot of the big chains for a fraction of the cost.

"Smaller retailers are really embracing it, with 100 signed up in the first month."

The company said the cities had been chosen because of their vibrant independent scenes and willingness to embrace new ideas.

Local ambassadors have been appointed in each location to work with merchants to introduce the technology and grow the Droplet brand organically.

With user numbers now at more than 23,000, there are plans already in place to build on the initial rollout by targeting another ten cities during next year.

Mr Aquarone added: "Birmingham was the ideal place to first test and roll out our app. It's a place that welcomes disruptive technology and both businesses and consumers are early adopters.

"This gives new ideas a great chance to flourish and we have certainly benefited from it.

"With the opening of Grand Central putting the city firmly on the map, I can't think of a better time to push our rewards platform and capitalise on the massive increase in footfall that is expected."