Ready for redstone power?
Step 1: Door
Place an Iron Door and a pressure plate next to each other. If it is wooden, then it will open with an arrow's weight. If it is anything else, it will only open for weight.
Step 2: Sneaky Boom
Set up a tripwire with string. Add a trail of redstone leading to the explosives. Walk on the wire and the redstone will light up, setting the TNT off.