Picked up this thing yesterday and it works great. YOu can use regular batteries, or rechargeable or plug in micro USB.
The only issue is the sensor is pretty short. One poster cut the wire and extended it. But it’s super cool, tells me right where to stop in the garage. Worked perfectly first time. Now I just worry I’ll catch the cable and rip it off.
STKR Concepts 00-246 Adjustable Garage Parking Sensor Aid, Dark Gray
I have always been a fan of a tennis ball hanging from the ceiling with a thin rope. You mount it so that when you drive into the garage you can stop right where it makes contact with your windshield.