Originally Posted by Damemorder
You know... trip wires can be made sensitive enough to detect silly string....
Yes, but then they become sensitive enough that they are exremely hard to set up without splattering yourself.
They're also fairly hard to make. You would have to make a mechanism, rather than just unbending the pin of a grenade and tying a string to it, or some such.
Also, if you're standing back outside the doorway while spraying into the room, you at least have some shelter from a blast, or a little distance from it.
In any case, it'* better than the usual way of finding them. :(