There are a couple calls for the auto park (Summon) and homelink features. I'm working on them now. But here's the gist of it:
trigger_homelink: lat, lon, token
autopark_request: lat, lon, token, action (start_forward, start_reverse, abort)
It looks like token is just your bluetooth device name, so that's pretty easy to fill in. There are also some fun autopark states in there, such as "panic", and errors such as "keyfob_not_present", "12_volt_battery", and "public_road". Based on the keyfob one, it looks like you need to have your fob in the car for it to work. When I try it with neither my phone nor my keyfob nearby, I get back {"response"=>{"reason"=>"mobile_homelink_disabled", "result"=>false}}.
I'll do some more testing on it, but it looks like the car needs to see a fob to make it all work, so that might be a buzzkill for a lot of ideas.