Tracking device to find drunk parent?

My dad is a drunk and sometimes he gets lost and I have to go look for him. I was wondering what the best and cheapest Tracking device that I could buy would be? He is perfectly fine with me putting it on his Truck, he actually asked me to do it. He wants it mounted underneath his car and out of his way but I'm not sure how they work though, and how good they are? I don't want to spend a lot of money on one. So what is the best working and most accurate one but cheap? He also has an iphone and I do as well, is there anyway to track his exact location from the iphones if I can't find him? If so, then how?

Tracking comes on most phones and you can go on a computer (or your phone) and see where exactly the person is. My friend had this same problem with her grandfather. There are apps you could use too if you have a smartphone.

Find my iphone is a good app, but you will need his apple account info and the phone will have to be on.

You can get GPS Tracking Pro if you both have android cell phones
Every tracking device you find will have a monthly payment of 20-60 dollars & a one time payment of 200-400$ for the actual device.

Here are a few I recommended:
AwareGPS
STGPS
and
3100INT

My family members use these to track there teens, I would say it tracks dads too.

Another note: My dad is an alcoholic too, it can be hard because you love them and don't want them to hurt their selves or others, Keep your chin up.

First off i would just like to say that the whereabouts of your drunk dad is NOT your responsibility. He is YOUR dad, hes supposed to be taking care of YOU. My advise to you is to ask someone for help. Whether they be a family member or a friends parent. Your dad has a drinking problem and should not be drunk so often that he wants YOU to buy a tracking devise so that YOU can go looking for him. He should at least be buying it himself.
Secondly, as for putting a tracking devise in his car, he should not be drinking and driving. I'm sure you love your dad very much and you would not want him getting into a crash and getting seriously injured. I think you should talk to someone about his drinking problem and all sit down together and discuss the fact that he may need help. I can't imagine how hard it must be to do this, but if you really really love him you should consider talking to someone. For his own safety and the safety of others. Not just on the road, for all you know he could get into bar fights on occasion.
I wish you all the best, and i know i didn't answer your question but i hope i did help a little.