Without derailing recent threads I thought I'd start a new one. The Garmin astro is illegal to use in the U.K. Until they sort out the frequencies. I've found a collar that uses GPS and Radio to show the whereabouts of the dog. It does have a yearly subscription but it is also a very good alarm system if you have dogs in kennels. You can set a proximity alarm and if it leaves the area it will ring several numbers. You get full mapping with it to use on your phone which you do not need a phone signal to use.
What do you think? Portable GPS Tracking Device, Portable GPS Tracking Systems - Retrieva Tracking