Thanks for all the replies. The product "Motion Detector & Remote
Alarm" on this site also interests me as might be a better solution
for us. Will see if I can get in UK/Ireland......avoid heavy shipping
costs and tax, etc.
Mum on heavy dose of fluid tablets so gets up regularly during night
to go to toilet which we don't want overnight stayers to be wakened up
by but this detector would wake us up if she wandered into other parts
of house such as living room or kitchen during the night, we could
just put the detectors in the rooms we'd prefer she'd stay out of
during night!
Ta,
DW