Over the past year, I have used X10 sensors on and off (as part of the "Home Alone" prototype). The batteries have lasted impressively. While X10 is not the future, it represents a cost effective "available now" starting point.
A new perspective comes with this reboot: I am less interested in the subscriber model (a website/server to aggregate the collected data for perusal and dispersal). I am (re)looking at GSM/SMS as a first tier notification solution (with email notification an option -- via Internet).
With that in mind, the proliferation of ARM based linux boxes is offering relief from the >$100 Intel SBCs I've been resigned to using. A Beaglebone/RaspberryPi (and their ilk) are not my targets. I want an industrial quality ARM SBC that can be trusted. A few are starting to appear.
If my system *has* to be AC powered (you can't effectively do wi-fi nor ethernet nor SMS indefinitely under battery power -- maybe a few weeks at best), then considering Microcontrollers (like the Cortex-M4) doesn't make much sense.
If I did a Cortex M4 approach, we are looking at:
- $12 board (start with an eval board)
- Hardwired sensors (and then build BT LE wireless nodes)
- A GSM modem
- Development using MPE Forth
On the other hand, if I did an ARM/Linux SBC:
- $60 board (Maybe the Olimex OLinuXino-MAXI board)
- X10 sensors
- A GSM modem or just "ethernet"
- Development using clang/g++ C++11
The BOM works out roughly the same, but with less work for the Linux SBC. In addition I can do development on my laptop and target my Intel NUC for the prototype (porting down to the Olimex later?)