I have been wanting to get one of these for a long time but now that I'm looking I am not finding exactly what I want. I sawa wireless controller but it appears to only fire off the shutter for a regular burst or with a 2 second delay. What I really want is one that I can program for a long exposure (like 20-30 minutes). Any suggestions? Trying not to break the bank either. Wireless preferred but I would be willing to use a cord if it works better.