Interesting. Very slick ad, nicely done. The impression I get is that each Flic (at $34) will perform one specified action. So if you want to be able to lock your car, unlock your car, start your car's heater, and open your garage door, you'd need four Flics. (Maybe double- or triple-tapping would perform other actions?
The reviews on Amazon (at the above link) are mixed. Apparently it works well some of the time, sort of works some of the time, and doesn't work some of the time.
Using your phone as a key fob, the phone is paired to the car. So for the Flic to work a a fob, the Tesla app would have to be willing to recognize and work with the Flic. My guess, the Flic will probably not work as a key fob for the Tesla, though Tesla could decide to allow it.