> Can you unlock your Tesla?

Yes but you have to use a third-party app for that, the official Tesla app does not have a Watch version.

> Also can you do navigation?

Yes.

Watch App for Tesla is also great in that it can act as a key, so you even get prox unlock with your Watch.

A few times I've forgotten about this, went to get something from the car without my phone, and been puzzled why the car unlocked lol