Any App developed by no matter who will only be effective if follow ip is effective. Let's face it, if contact is by mobile phone this can be answered from anywhere. Only if the your phone is being tracked will the system know if you are at home when answering, that's if there is a follow up in the first place. An awful lot relies on people's compliance which we all know just isn't happening. Neighbour's sister arrives from Spain for mother's funeral. She chuckled when asked at the airport for her mobile number and contact address. End of isolation, no phone calls, nothing. She knows when going back to Spain she will be visited to check on her whereabouts during her isolation there. It's a farce the whole system.