Yes, as would using an app to calculate the fare provided the basis of calculation can be quoted in advance on request. That's how mytaxi's hackneys work here and how Uber's minicabs work in London.
No, taxis, hackneys and limousines are allowed to use apps to accept bookings. The law was not changed to allow any drivers interact with their telephones while driving. Under current legislation you could use a device that isn't capable of making or receiving a telephone call and argue that, as such, it is not a telephone if prosecuted for using it while driving.