There is also a proposal(hopefully merely a rumour) that compulsion may be needed in order a tracking app may work. Also that those that do not have a phone capable of using the app may be given a suitable tracking device. Interesting concept that compulsion may be used to overide existing freedoms. Having worn a satellite tracker in dodgy spots I can appreciate there are two distinct sides to the coin. I think the idea would require a lot of selling otherwise a large hammer might have a meeting with a phone.