If you have a BOC outlet near you, they used to stock a digital thermometer with an alarm, measures to .1 deg celcius with 1 second updates and a stainless probe on a 1m lead. You can set a low alarm and a high alarm as well, very handy, lets you know when you get to your strike temp, and can be used to monitor your mash temp. Good for that water purifier too...
Mine cost me $25, not sure if all BOC's stock them, but wouldn't hurt to ask, they are a comparable price to most, and quite adequate.