In a huge parking lot if I'm going to be gone a while I'll geo-tag my car's location using the maps app on my phone. To get back to it I just choose the "walking" option and it'll guide me right to it.

 

I have SmartTop for my c4s, and it allows you to program a sound for locking/unlocking. Beeps once to open, twice to lock. SmartTop is pretty fantastic in general (no affiliation), but I like the beep.

I also think it is pretty weird to have only one button

 

Ben, Ben, Ben great idea except for two things. First, I work in the tech industry, I don't use their products. Second is real men would rather roam lost than cheat and get help from anyone or anything.
I tried that once in a DC hotel parking garage. Worked great except I walked back and forth hearing the lock horn get louder and fainter. Turned out I was one floor too low. After that I gave up on tech.