I have just fitted a tracker to my explorer and after a couple of weeks understanding it and setting it up ,i can honestly say its extremely impressive for the price .
it costs between 40 and 50 quid and holds a simm card,sd card, and comes with two batteries although for a tenner you can hard wire it to the bike.The simm card allows you to text it and it will text back a link to google maps to let you know where it is and the sd card allows you to trace the history of the vehicles journey and stops. i didn't think it was as accurate as it has turned out to be but i used it today and it picked up all my traffic light stops. its positioning is within 5 meters of its location .Its called a REWIRE SECURITY 102-nano theirs loads on you tube about them. i am probably a bit late cumming to the party on this subject but for what its worth i highly recommend it.