I use mats to heat my vivs as it suits me. If you are using a mat an on/off mat stat will do the trick. These do the job just fine (once you have adjusted them correctly) although if you have the extra funds available a pulse proportional stat will be far more accurate and fluctuate far less.
Hope that helps
Cheers
Steve
1.1.0 Amel Corns Colin and Xena 1.0.0 Dog Talan 1.1.0 Cats Wotsit and Willow 1.0.0 Ferret Chaos