Not because I am being critical, but because all the discussion got me thinking: I used to use this thing called a boulder buster made by Swartklip in S. Africa. It was a big steel tube with a barrel on one end and the other end unscrewed. It was attached through a mat of woven rubber. You had these boulder buster carttridges that were basically purple coloured centerfire 12 gage shotshell things. You drilled a hole in a boulder (not little ones, but like one or two times the size of a truck). You drill a hole with a jack hammer (privided you do not fall off the boulder trying) and fill the hole with water. Drop in a couple of the cartridges, and then the barrel of the boulder buster went in the hole. A rimfire 12 guage shotshell like thing went in the top and the top was screwed on. There was a long lanyard, and at the end was a bit of thin cable with a steel ball at the end. The steel ball went into a slot in the side and into a grove in the firing pin, then rotated around with the cable sticking out the top. There was clearance for the cable, but not for the ball. When you pulled the lanyard, the firing pin would be retracted until it came out far enouhg to release the ball, and then it would fire. The boulder would shatter, and the whole device would go 50 feet into the air with the rubber mat flapping like a sonarless bat before it piled up in some impossible to extract place between boulders.
The ignition system was simple, easy, and safe, other than the fact that the lanyard was made from a yellow floating rope that stretched 3 feet when you pulled it, causing the heavy steel ball to come whipping back through the air and hit you in the face.
Of course, you cannot get lead line (shock tube), but I wonder if a shotshell primer shooter would not work well for you if attached solidly? You could use a hair pin as a safety that can be easily pulled out with one lanyard, and then fired with the second lanyard. It takes 209 shotshell primers, so it would be cheap to use, and just take a bit of modification to set up.
Edit:
Nevermind, I forgot how expensive they are. I remembered them being like $60, but I'm never the one who pays for them . . .
http://www.idealblasting.com/idealhandstarter.aspx