Remote start is, in my opinion, never safe, and an ill-advised feature (but your opinion may differ, there is obviously a market for such a feature or GM wouldn't build it in).
I would personally have the manufacturer disable it, and have them confirm in writing that it is disabled, just to be on the safe side liability-wise myself.
There is not much to gain from being able to perform a remote start, other than "being cool", and warming up the engine. Which, arguably, is a bad thing. It may seem like a comfort feature especially if you live in a quite cold area, but there are better options (aux heating) if that's desired.
From an engine's point of view, needlessly running idle while cold is just as bad as running full thrust. Neither one is something you want to do if you love your engine.
To add to that, exhaust (in particular NOX and fine dust) is maximized running idle on a cold engine.
Some safety considerations against remote start are:
- Car not just starts, but actually starts driving, runs over somebody. This is something that I remember happened a couple of times due to a defect in the 1980s with... I believe it was Audi (don't nail me down on that, might have been a different company). Now, this defect is a feature.
- Car starts at an inappropriate moment, for example when you are bent over the hood with your head and hands inside, and you accidentially press the "start" button on the clicker inside your pants' pocket, or your phone does a kind of "ass call". Or, you know, "just because". Software does have failures, and such things do happen.
- Your phone (which is hopefully not an Android phone susceptible to DirtyCoW, such as presently all Android phones) is taken over by a malicious app. Some "cool kid" in another country has a fun time starting your car, too bad for you that something tragic happens. Someone is injured or killed with your car and wants indemnity. You are the only person one can lay hands on. Good luck.
- The car itself, or a server at GM is hacked. That's much less likely than the previous point (the previous one is really serious), but still entirely possible.
- Car starts -- legitimately, and correctly -- and runs idle for a few minutes, and causes a fire due to e.g. the catalyzer's heat lighting a patch of grass. Since nobody is around (it's remote!), nobody gets aware of the problem until way too late.
- Car starts -- for any reason, legitimately or illegitimately -- in a sealed environment (garage?). The next person entering the garage 15 mins later (you, quite likely!) dies of CO intoxication. Due to CO's very high affinity to hemoglobin, taking one or two breaths in such an environment is often enough to be inescapably lethal. No, you can't run outside as soon as you notice. Your hemoglobin simply won't take up the oxygen once loaded with CO.
- Liability: In case anything happens (including hacker attack or defect, or even an accident where someone falsely claims your car started on its own) -- can you present credible evidence of your innocence? Do you even have access to anything like a log file? You can bet that GM will have their army of lawyers and will sufficiently cover their assses. How big is your army of lawyers?
In addition to being "inherently not safe", it may be "not legal" to use remote start for a variety of reasons, among these local laws which may forbid the use in public space (in fear of bad things happening). But also, for the same reason, it may be forbidden e.g. by company policy in the parking lot at your work place, etc. etc.
The only "undoubtedly legal" location to use remote start would be on your own property, and even then you cannot be 100% sure.
For example, in some countries (including e.g. my place) it is explicitly forbidden by environmental laws to have the engine run idle "to warm up", even without using remote start. It is also illegal to have a vehicle unsecured-ready-to-drive, which is arguably the case when the engine is running with no one around.
