Also more recent (over at least a couple of years old now I think) Mercedes keys detect motion and stop transmitting if left still for a couple of minutes, so you don't need Faraday pouches or double click. When you pick them up / move them they start transmitting again.
Hopefully this helps others out as lots of people with recent Mercedes don't realise this and still use pouches or double click. Simple to test - lock your car, put the key on the floor, wait see if you can open it, if not nudge the key and try again, repeat until you are happy (or not if it does not have it).
