If you're looking for a digital remote thermometer I have the Acu-rite from home depot and it's been working well. Some people have had issues but mine has been working flawlessly. There's a thread all about it.
Have had one for a month, first off, the USB can be used with you computer to upgrade the software, the first one I got, the sponge that was supposed to keep the sensors damp had dried out, had some trouble with it, after a couple days trouble shooting, I drove down and they replaced the entire unit, no problems, never had a problem getting them on the phone either, massive shop, not some fly by night company. Version 2 is the way to go, I think that it is all you can find now anyway, future upgrades are supposed to include a pressure reading on your system so you know when to backwash, cannot wait for that one.
Only thing I dislike is there in no internal battery pack, unit must be plugged in or it resets and takes a couple hours to get spun up again. other than that I have found it to be fairly accurate by comparing to chemical tests.