Can anyone recommend a Safeguard approved tracker with a good iPhone app ?

[Clattergate]

It seems to be a bit of a minefield... just been looking at "Tracker" which has an appeal but there is no demo of the app... and apparently they alert you by email of a "movement" ... is this true ???
Anyone got experience of the Vodafone tracker ?

 

[ceejayt]

I have Scorpion - the app is good, I am happy with it