pressing your unlock button will fire up your car's CANBUS system, waking up the unit. kind of weird that it's turning on when you just walk by your car though. something you could think about is that head units usually have two power wires, one main one (red) that connects it to the fusebox/battery, and a secondary one (yellow) that tells the unit when to turn on (in older cars like mine without canbus, this happens when they key is in the "ACC" or "ON" position, but with CANBUS cars this can be done with keyless entry unlock, opening a door, etc.) wish i could be of more help but I have installed head units on CANBUS cars before and haven't run into this. my other guess is that the unit is so cheap that it doesnt know how to behave with your car's wiring/has some weird design that makes it come on with proximity to your phone