Hey, this idea sounds great and I hope that we can do this!
What I do not like about the other apps is that they are not working for me. It can be because of my settings, but I always turn GPS on before I start.
In my opinion, the design could be ok and does not have to be perfect if it is working.
For the money, you can maybe use pages like Kickstarter? Only if there are enough people who would donate, I don't know how those sites work..
Because the problem of most working smaller sites or apps is that there are no spots marked in Germany, or if so only in Berlin and Hamburg, the biggest cities. To prevent that, The app should have as low costs as possible.. Another idea might be to contact sites with spot maps and ask if one could use them for this app, so the app would start with a lot of spots and not with nothing

I hope you understood my point, and I hope I can help