I've drilled a cooler for one of the Thermo-thingies for an HLT. I still haven't gotten the thing to stop dripping. I didn't bother on my mashtun. I just measure temp at the beginning and end of mash. My 10 gal Rubbermaid cooler holds to a degree or two over an hour.
Primary: , Boddington's Clone, Mirror Pond w/Marris Otter
Bottled: Fullers ESB Clone
Kegged: Mirror Pond Clone
Drinking: BM's Kona Fire Rock, Dead Guy Clone, Alaskan Amber Alt Clone, Firestone DBA Clone, Magnum/Crystal IPA
Next up: Burton IPA