The APO3 saves a lot of hassle in turning the gps and radio on and off automatically. I used to use a relay hooked up so that when the car started it turned everything on. But this had a flaw because when the car started it would shut off all the loads except for the starter and my relay sensed this. So the radio would come on and then off and back on. There is also worry that during the starting process there might be voltage spikes.
The APO3 solves this because it only comes on when the voltage criteria rises to a point after the car has started. When you shut off the car, it senses a certain voltage that indicates the car is not running and then starts the countdown timer that you can set for different times. In real world running errands around town, the APRS system stays on unless you stop for a longer period then it will shut off. This keeps the cars battery from deep cycling which is bad.
The only problem I had was my fault. I used the bypass switch to keep my things on and forgot to switch it back to timer mode. The LED would have told me it was still on but I had something covering it.
The APO3 is well made and well worth the cost to make a mobile station automatic and save the battery at the same time.
WT9MRating: [5 of 5 Stars!]