My wife is working on a green roof research project and needs to log temperature and humidity data at 8-12 locations. They are/were planning on using the HOBO U23 Pro v2 Temperature/Relative Humidity Data Logger from Onset Computer Corporation ($179: http://www.onsetcomp.com/products/data-loggers/u23-001). They look like fine little data loggers, though perhaps not perfectly suited to the field conditions in which they'd be used, but they also require an Optic USB Base Station ($124), a Coupler for HOBO Pro v2 (Included), and (probably) a license to use the proprietary HOBOware Pro Software ($99). 8 of these would cost ~$1,700 (USD), be limited by the hardware and software, and not be the best choice for the use case (the better solution is much more expensive). This is my attempt at more reasonably priced, expandable, easier option.