I was looking for a reliable thermometer to hang on my backpack.  The Ultrak 830 does seem to be well built and reliable.  It is interesting to check out the heat index and humidity although it wasn't on my 'things needed' list.  

The Ultrak is larger than I was expecting.  It's three inches in diameter.  That's a good size for a stop watch --which it has, but a bit larger than what I was looking for to hang on my pack.  Nevertheless, I have it there and it works fine.  It comes with a lithium battery and a photo cell so I am hoping that the battery life will be long and not necessitate frequent battery changes as my last thermometer did.

It is very easy to program.  

The time piece is accurate and the unit defaults back to the time after a couple of minutes on the temperature.  I takes only one button click to bring up the temperature.  The unit also has an alarm on it.  I don't think it's loud enough to wake me from a deep sleep, but it might be useful to remind me of something while carrying it during the day.

All in all it is a cleaver gadget that does seem to be well built.  I haven't had it long enough to truly say how reliable it will be but I think it will do fine.