Here is a possibility for mines.

I move a unit into a mined location. Your mine attaches itself to my unit (unbeknownst to me).

Here are some possibilities at this point:

1) The mine stays attached to my unit until you (on one of your turns) issue a "remote control" order for it to blow up. A "dumb" mine.

2) The mine never blows up on the turn that it becomes attached to a unit. However, on subsequent turns, it blows up if a "trigger" condition occurs. For example, a "smart" mine could be set to blow up if the unit to which it is attached attempts to move or fire. Of course, this would allow the player to discover which units are mined - perhaps the mine owner could turn automatic triggering on and off, and would turn it on only if s/he felt that the automatic trigger was worth revealing the mine to the opponent. In fact, a unit with a "trigger mine" should be marked for all to see (after the turn in which the mine is attached).

One could just forget "automatic triggers" and simply go with option 1 above. It's certainly simpler and less problematic.

what about reveling and disarming mines?