Monitor your "Independent" Grandmother for under $200 (hardware cost)

I'm looking into appropriate ARM based devices for the base station, one with good wi-fi coverage and enough memory/horsepower to be the base station. The current contender is about $75.  Cheaper ones can be had for under $50, but I wanted one with a good antenna.

Pair that with a few sensors and you can get started for under $200. What would this get you?

Let's assume X10 for now (until I get my Bluetooth LE sensor project going).

Let's also assume an apartment or condo...

You'll need

• 1 Wi-fi Base Station ($75)
• 1 X10 USB RF Transceiver CM19a : (ebay *new* ~ $20 each)
• 1 Door sensor, DS-10a or DS-12a : (ebay *new* ~ $13 each)
• 4 Motion sensors MS-14a or MS-16a (ebay *new* ~ $12 each)
• Living/Dining Room
• Bed Room
• Kitchen
• Bath Room
• 1 USB temperature probe (~$15 Amazon, ebay, etc)
• 2 "I need you now" buttons KR-15a (ebay *new* ~ $8 each)
• Mounted Next to bed
• Mounted in Bathroom

So, to monitor Grandma,  you'll need to buy around $188 in hardware.

With this hardware, you can monitor stuff like:

1. Did Grandma go to bed last night?
2. Is Grandma in bed unusually late in the morning?
3. Did Grandma leave the apartment (wandering...)?
4. Did Grandma eat breakfast, lunch and dinner (activity in kitchen followed by dining room)?
5. Did Grandma leave the kitchen stove on unattended?
6. Is Grandma in the bathroom an unusually long time?
7. Does Grandma need assistance? (Pressed Big Red Button)

This isn't a scary amount of money.  What do you think?