Home Alone "elderly monitoring" Project reboot coming...

A much needed reboot of this project is poised to happen.  My mother-in-law is moving in and I am going to need a monitoring system for when she is left alone in the house.  In particular, I am concerned about the "wandering" potential (i.e. leaving the house).  I am less interested in the stove monitoring (which introduced a number of manufacturing show stoppers for the project).

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?)

So, anyway, I am still mulling this over, but in the next few days I will be making a definitive decision on direction.