pager/phone to caregiver

["bill" <williams12345@xxxxxxxxxx>]

  I am looking for something my father can use to page his caregiver.
She is in the same house, but could be talking on the phone, watching
TV, etc.
Requirements:
1. It should be small enough to comfortably wear around his neck 24
hours.
2. It probably should have only one button.
3. It should be able to transmit 100ft through walls dependably.
4, It would be nice if he could also talk to the caregiver.

The x10 KR15A:
1.  Maybe, not sure how big it is.
2.  Yes
3.  Based on my experience with UR19A, HR12A the range is dependably
30 ft through walls.
     I suppose we could have multiple TM751 receivers, but that may
create other problems.
4. No

I see that there are services like lifealert.com that provide a
pendant which calls a service
and then he can talk to them via a speaker phone.  There is a monthly
charge.
This is obviously not what he needs, but parts of it seem appropriate.

Are there any products that meet 1,2,3 and maybe 4?