There are a few people on here that put dimmers on their heating devices and they work fine, but it's still a good idea to run your flexwat off of a thermostat.

As for the hygrometer, I know that another few people use the accurite thermo/hygrometers. They measure temperature and humidity on the unit itself, and it also has a probe to measure a second temperature. About $12.00 at Wal-Mart.