I have purchased around 6 of them and the best one and of course the most expensive is a Fluckers available at Pet Smart or Petco. They are made for reptile habitat and are designed to be kept in humid climates.
You can also get a fairly good on at Walmart. The Accurite is pretty reliable but a bit large for my needs. I have a small incubator and it takes up way to much room.
Don't get one that is designed for a humidor for cigars. I found those to be very unreliable and I believe others have as well.
i got mine at wal mart too and so far it has worked pretty good. it is both a hygrometer and a temperature gage. its digital and seems to be working good. plus it will giv eme the highest temp and lowest temp snce i last checked it. which is good for when im not home.