BRILORMAC AlexB wrote: "I wonder how long it would take to build such an app myself"
If you are a skilled developer and have unlimited time to devote to the project, figure on 1 to 2 years. If not a skilled developer, 3 years plus, and if not programming full-time it might be 4 years. Undoubtedly these time frames are too long for most to self-develop, but one-person development takes lots of time. I would suggest encouraging the developers with incentives instead of bludgeoning them in public. While I have little sympathy for unresponsive developers, I also believe developers want the financial reward that is often unreachable selling shareware at $39 USD.
Disclosure: I'm a Mac developer and a software engineer for over 35 years, but I am not affiliated with the "Money" software in any way.