Can't see how having ignition on/off can work, you don't put a key in the ignition today, you simply have them about your person, as to being able to start the car, well can do that anywhere in the world, don't have to be sitting in the car, OK should not start your car using the phone while on a public road, however you can physically do it.
However unless you press the start button, the gear selector knob will not raise, so if you started car with phone you could not drive it away, so you can open door with phone check the fuel with phone, check location with phone, and start engine with phone, but you can't drive the car with phone, you need key fob for that.
Also when you drive the car the on board computer logs the trip, so easy enough for the law enforcer to see if the car has been driven.
I am not sure about the use of a phone in the car, as although hands free, the phone is not fixed, likely in my bag on back seat, but that makes no real difference as well as using the cars hands free, I can also use my watch.
So if you have parked your car and are riding your bike home, if you can start car from your bike, can you be done for drunk in charge of a bike and a car at the same time? For interest car is a Jaguar XE.