I have a couple of Accurites and they've been pure garbage. I always hear people rave about them, but mine show a 30-40% difference in humidity between the two, and the temps are always 10+ degrees off...at least. I don't know if I got bum ones, or they were damaged somehow, or what...
A good Infrared Temp gun is invaluable. I can check every tub in all three racks in about a minute and I can rely on the readings. Lowe's/Home Depot usually have them fairly cheap.
As far as measuring humidity, I gave up on the Accurites and just wing it. Being on the east coast, humidity isn't really an issue so I'm lucky there.
Best 20 bucks you can spend http://www.lowes.com/pd_73790-56005-IRT207_0