I like the interface and config of ProcessTamer, but just changing the priority doesn't cut it for a stupid program that I have to use at work that was written like a DOS program in windows. It takes 100% CPU usage to sit around and wait to read a sample from the serial port. Battle Encoder Shirase limits the CPU usage, but the interface doesn't allow for more than 3 programs to limit, or a way to watch more than one program. I also have found PsSuspend, but it won't limit a process, just suspend or re-enable.
Thanks,
-Nick