You can by-pass the "Clutch IN" switch and use the Parking brake switch as a fail safe, if parking brake is not set then remote start won't work.
That should prevent vehicle from moving if it was left in gear, assuming your parking brake is working, lol.
Starter couldn't turn over engine if left in gear with brake set.
But as a for a neutral sensing device for Ranger manual trans, no.
The best way I saw was a remote start system hooked up to the keyless entry system.
You would set the remote start while engine was running, when you turned off the key engine stayed running until you exited the vehicle, closed door and pressed the Door Lock button on the key fob, doors would lock and engine would then shut off.
So vehicle would have to be in neutral when you exited it.
If door was opened again before remote start was activated, it would deactivate remote start, because trans could have been put in gear.
So no, no easy way
In later models I think you could add a "neutral towing" switch for the 4x4s, this shifted transfer case into neutral electronically, so vehicle could be flat towed behind RVs.
This would lend it self to a remote start quite well I think.
Block heaters aren't bad