I have to find the link somewhere but it's an analog one that you can calibrate. The acurite one from wal-mart works but I can tell you that it's off.
As far as defrosting goes what I do is take out what I'm feeding about 5 hours ahead of time. Then for the last hour I leave it under a heat lamp which stays cranked about 100ish. Then about 20 mins before hand I flip everything over in the plate so both sides get heated that way it properly heats the inside. Then when I get ready to feed I take a hair dryer and hit the rats with it for about 30-45 secs and have it aimed in the direction of my rack. That brings most if not all to the front of the tubs. Just a warning feed with tongs and don't put your face near the tub. Even my little ones who were born this year have killer feeding responses and almost all of them will come out the tub if you're near. I just hold the rat for them but usually I put it on the side of them so they don't strike out of the tub. Then once it's all said and done you're good. When they were babies I started them off on rat pinkies because I wasn't sure if they would take to frozen thawed. Then after that one meal I switched them to rat fuzzies. Then straight after that I went to rat pups.