Today's explosive device is....trip-wire!
What is a "trip-wire"? Well, it's a wire (or laser beam) that's tied between 2 points (usually sides of a doorway) to trip someone (or set off an alarm, or blow them up). Admittedly, it's a bit of a recycle from the proxy mine, but simpler. In this case, we'll make it a laser tripwire across a doorway.
You'll probably need 2 events: 1 for the projector, 1 for the beam.
the projector goes on the wall, the beam event goes in the space between the walls/doorway. You can have some shut off/erase business with the alarm, but we'll skip that (I'm sick of talking about that). The beam will be a parallel process; the custom movement route, you set it to go back and forth as fast/often as possible (since it's likely only 2 squares, it'll be pretty fast). Create a 2nd event page for it, but have it as player-touch (you don't need a move route). What goes in the event box is the consequence of tripping it (alarm, explosion,etc).
At this point, I think I've covered just about every explosive device I can think of.