Inside telephone wiring in old house...

A seventies house with CAT-1/CAT-2 telephone wiring with outlets in most rooms; what can be implemented ?
There is no landline telco service in use any more.
Security? intercoms? sensors for something? ambiance music? power outage lighting? 5V distribution? What else can be a really interesting use ?

Depends on the number of conductors, I used mine for the hi-speed internet feed from the basement, also a Android TV (Stream Team) box to use cable connection instead of Wi-Fi.
Max.

Probably four conductor, red, grn, blk, yel, even though only the red-grn pair was used in most residential installations...