I had one of those pictured above and it went pretty wonky after a few batches, bought another, and had the same thing happen again. Then I bought a Thermapen, which I really like and have been using for quite a while now.
I've been extremely happy with the thermapen, and as such I have recently gotten a new handheld mini thermocouple from the same company, along with a couple of different probes so that I can use it for various purposes. Waterproof probes for monitoring mash and fermenter temps, instant-read stick probes for checking grain temps, etc.
It's might be more than you're looking to spend, though.