I like the look of this and would be fine with the installation I think. How would I know if I have the 3v supply in the cable or need the battery option? I have a Zappi V2 if that makes a difference?I purchased a 'Tesla Retrofit Button Kit' from here:
Tesla retrofit button kit - evChargeking
Really easy to fit to a type 2 plug if you're handy with a soldering iron and can drill one hole. All the instructions are on the website and the mod takes about an hour.
It's so handy, no more having to unlock from inside the car. Money well spent.