I need a recommendation for a valve here?

So yea I have this little project I'm working on. So basically I made an improved version of something I saw on the internet and want to improve it further. So since you probably don't care what it is and I really don't want any of my ideas being stolen, here is the basic thing I'm doing. So I have a hand pumped air compressor (this thing relies on size, not power) and It is connected to a about 1/4 inch tube which has a valve on it. All of that is part of the actual compressor. Next there is a few feet of 1/2 inch tubing which houses a ball that is shot out with the air pressure. So what I need to do it is to add another valve (have to keep the smaller, hand operated valve) somewhere in the 1/2 inch tubing that can quickly release all of the pressure by it electronically opening. So what I need to know is what is this type of valve called and how much does one cost?