Mark,
Three years ago we installed fifteen Hobo U12  units (records temperature, relative humidity and light levels) in exhibit areas scattered about the airport system.  I walk around quarterly with a laptop and a cable to download the contents of each and re-launch them on site.  They have been very easy, reliable and they are not expensive.  The software has been good, too.  If they record the type of information you need to have I recommend them.

Onset Computer Corporation: http://www.onsetcomp.com/products/data-loggers

Good luck,
Sheila

Sheila Kollasch, Museum Assistant
Phoenix Airport Museum
3400 Sky Harbor Blvd.
Phoenix, AZ 85034-4403
602-683-3647
FAX 602-273-2702
[log in to unmask]

“The most beautiful thing we can experience is the mysterious. It is the source of all true art and science.”—Albert Einstein