Hi Rob,
The RF transmitter for your thermostat is interesting and perhaps useful.
However, I would avoid using any low power RF signal around me, except for the moments I really need to use the smartphone for data/WIFi/bluetooth etc.
There is scientific evidence with perhaps more than 1000 published scientific papers (I'm working in this field for about 20-30 years now) that low power RF signals, far below the levels causing the thermal effect explained by SAR (specific absorption rate), are causing weird and unexpected problems to both plants and rats (please read also humans). Those power density levels are near and below 10mW/m2 which is extremely low.
If you're able to send short bursts of RF signals Manchester encoded followed by long periods of RF silence, that's ok but either I'll not stay all day near any kind of transmitter: GSM phone with WiFi and mobile data permanently connected, near any laptop with Wifi turned permanently
on
or never use a handsfree
Bluetooth (not talking about bluetooth headset).
If you are interested in this field please take a look at the recent two papers we wrote (but you may read hundreds of papers with pro&con conclusions as I already told):
thx,
Vasile