I think the limiting factor is going to be the energy required to turn over the mechanical starter--same as with a keyed ignition.

A few years ago I looked into a remote starter for my car, but didn't end up buying one. The installer said that he needed a "chipped" key so the remote would work, without my key in the ignition. My impression--and I should have asked--was that he was going to put the chip next to the ignition switch, so that the car would recognize its presence and that, once that was satisfied, if I wasn't using the remote control, I could use an unchipped key.

Edit: anyone tried this?