YouTuber jryanishere seems to have gotten Alexa her driver's licence, thanks to a few snippets of code, a Raspberry Pi, and an OBDLink (which is some sort of Bluetooth scanning tool that works with GM's proprietary controller area network). Having Echo in the car doesn't seem to be necessary, so much as it made filming the whole system easier — meaning this might be a legitimate remote start that could make those chilly winter mornings easier, at least for one industrious person.
Indeed, it appears buckling Echo into the passenger seat was mostly at attempt to ward off the usual army of commenters decrying anything hard to understand as being fake. However, the entire build process is covered in excruciating detailed on jryan's blog in a five-part series. I may not understand Python or known anything at all about car hacking but it seems legit.
Alexa, get in — you're riding shotgun.