trailer tracking device gps

hi,
We are small fleet with 4 trucks and looking for tracking device for trailers and one that cost less, because alot of times trailers are loaded and parked in the yard over the weekend.

I seen one at radioshack this week it's $12 a month but have to buy the device for about $100, i'm not sure on the battery life on it.


Any recommendation would be appreciated.

 

No we have drive van's but this is something good if i ever get into reefers.

 

I called all these and most of the require tractor to be hooked up and provide electrical current to be turned on. I'm looking for battery powered where if trailer moves out of my safe spot i should get alert that some activity is happening and i can verify it's one of my driver or a theft.

 

I don't want the one that will turn on if it's plugged in, because if someone will steal the trailer i can't rely on them plugging the electrical wire in, trailer can move with just releasing breaks lol. I'm looking for something that can tell me if the trailer is moved out of the yard and alert me especially on the weekend because we don't have security guard there.