Hi,
I'm a mobile developer from the UK. I specialise in android development, but I am also adept at Swift for iOS.
I have previous experience with project timer based apps - my most relevant project being an app used to clock in and out of work, and track what projects you are working on (including retrospectively). This was ultimately used to work out payroll, and also to bill clients.
The reason I quote 3 days is through past experience acceptance can take a while even with small projects. I would expect to be delivering the APK at some point tomorrow with a day for acceptance. I will return the source code to you upon payment.
As an aside - have you thought about putting the app on watches? I have a lot of experience with android wear and would be able to work with you to do that. Perhaps setting a list of projects in the app, and a simple start/stop allowing you to pick from the list on start.
I look forward to hearing from you soon.
Scott