Myself, along with many others suffer through this problem every day particularly in neighborhoods where driveways and/or garages are not ubiquitous.
What it does
This design does not only locate parking spots that are available, but also has the ability tell you if your vehicle(motorcycle, car, or truck) will fit in the spot.
How we built it
We used Arduino just to have a programming interface(in C/C++) to manipulate our own custom circuitry which was built on a separate breadboard and parse the circuit's digitized inputs so the information can be comprehensive to the user.
The main challenge we ran into which consumed a lot of time was figuring out the appropriate output pins for Arduino Analog to Digital conversion since we were dealing with square waves rather than sinusoidal waves(so a computer can process the input.)
Accomplishments that we're proud of
We were able to figure out everything we planned on doing in the beginning(along with some extra ideas for expansion as we were working on it) and was able to not only successfully program a solution, but realize the solution using circuitry(true for the expansions as well.)
What we learned
Patience is a virtue and never giving up truly pays off when you finally figure it out.
What's next for Parking Space Locator
Move on to Hackathon 2018 final round and hopefully win. Also, developing the app that works in collaboration with the sensor we designed.