What I plan on doing is putting in a pressure relief valve using a manual boost controller (we use them on turbocharged vehicles).
Simple ball and spring design. As pressure builds up, it pushes the ball and spring down a barrel until finally the pressure pushes the ball past a relief hole. They are fully adjustable from roughly 5-30psi normally, so on a low setting you will bleed off excess pressure but still retain pressure in the system and using a simple electronic solenoid set on a timer you've got a fully automated system out of the DIY.
Speaking of which, if you want to know how much pressure your system is creating, you can put in a small manual air pressure gauge into the mix as well (< $20), once again super cheap on ebay and this will tell you when you're running out of CO2 and help dial in your system.
At least, this is what I plan on doing in the coming months. I can build a diagram if anyone is wondering what in the hell i'm talking about.