I really want to build temperature monitoring sensors, but this seems REALLY expensive per-unit.
I was thinking xbee + the dalsemi temperature sensor. I don't think you even need a cpu of any sort in there, since the xbee can do a little bit of the work.
Do you need them all in the same location? If so, you could use multiple sensors per device. Or, leave out the LCD... once the device is working, you shouldn't need any display. Or you could make that part modular and plug in an LCD only when you need it.
We have some temp sensors setup to monitor the temp of our server rack (poorly ventilated area), and the box we have takes 4 temp sensors (and a few open/closed sensors like power/security). It cost us around $400 for the entire setup. However, it looks like I could have made one for much less...
I was thinking xbee + the dalsemi temperature sensor. I don't think you even need a cpu of any sort in there, since the xbee can do a little bit of the work.