First up, a plug for Opto. We do make wifi brains, EB1-W and EB2-W. Our smallest rack is 4 modules, so that ends up a pretty small box when you throw in a 5v PSU. No question it would be quick and clean with (at the very least) these two sensors.
Having power at a few locations would make things work a LOT smoother... as Im sure you already know. But, you said you don't have ready access to power at these locations, so that makes things a little tricky.
I'm not sure what sort of transmitter I'd go with. You have one sensor that outputs millivolts and the other serial data.
Also, the 10HS draws 12mA... that's pretty solid.... If you can get away with turn it off and only turning it on once every 30 minutes or so to take a reading, but then you are looking at having some local control.
If you cant do that, then you are looking at a good sized big battery, or swapping batteries pretty often.
The serial at .3mA and 25mA when sensing is a bit better, but then you have that pesky serial data to deal with (easy if its hooked into a SNAP-EBx-W).
Here are a few milivolt transmitters;
Cheap version; http://www.monnit.com/Products/Wireless-Sensors/Commercial-Coin-Cell/900-MHz/Wireless-Analog-Voltage-Sensors
Are you friendly with soldering irons and can home brew your own? http://www.makershed.com/products/wireless-sensor-node
Note, I have not used any of them, just been Googling and reading around....
The serial is a lot more problematic....
These guys were next to us in a booth at a trade show; http://gridconnect.com/usb-to-serial/wireless-serial.html
Don't know anything about them (the guys seemed cool).
Anyway, you get the idea. Is there a transmitter that can do say 1 chan analog and 1 serial and use very little power? Lets know if you find one......
Also lets know what you end up figuring out. I am really interested in wireless stuff and Im sure others would be curious to know what you ended up running.