Might be cheaper to use a GPS GPRS tracker. It is the same as the collar you are looking at, but without paying a subscription to the company. It will send you a text message as often as you want it to with longitude and latitude. You can then enter this into Google Earth if you have a 3G signal to find the location. I have a subscription version with some kids when out walking, but have found them quite unreliable.
http://www.ebay.co.uk/itm/Waterproof-Global-GPS-Tracker-Tracking-Device-4-dog-child-aged-pet-kids-SOS-GSM-/251187303569?pt=UK_Mobile_Home_Phones_Other_Phones_ET&hash=i