It's 100% right that it's up to the company to decide if they allow drivers to do this and I'd guess that with ours, probably less than 20% allow it. Personally I think its a good option but far too many company owners make snap decisions based on assumptions of of how it could be misused and so completely miss the potential benefits. It does create a whole raft of possibilities for drivers to try and cheat, all of which need to be locked down if it's to work correctly.
We were first asked for this by 300+ hackney fleet who claimed to have the biggest load a cheating bu**ers in the county (but they all say that!)
It was like opening a bloomin can of worms and it took us months to close down the loopholes. Can't ever guarantee that someone won't ever find some way round things but there's always the turn it off option for anyone who finds a way to cheat while we close that one down as well!
Bill
Detecting if the phone is in the car is the easy bit btw!