Anybody hacked a cordless phone to provide short range radio control?
DTMF generators already built in, if you're lucky enough to have them
go from base to handset via the "intercomm" function.  Add a DTMF decoder
where the speaker used to be and you should be able to get 12 functions
"easy."  These days you can get such phones in a variety of ranges and
with 'encrtyption' as well, although you may quickly leave the "bargin"
area where the phones have a price advantage...

(Most of a cordless phone should work fine off a DC power supply with no
actual phone line, right?)

BillW