If you are into hands on, you can use the Arduino set up to make a custom control. Not sure about the Mac compatibility though. There is plenty of documentation and examples of the programming on the net. Plus the parts are very reasonable and there are many configurations available. Much more hands on though.

I program and build automated control systems 5 days a week. We mostly use products from http://www.heapg.com. An XL100 series would be pretty affordable. It can datalog to a microSD and it has a small display. I believe it is around $300. If you have any specific questions let me know. I should be able to make something up!