Is the wire open or shielded, BX or conduit, carrying AC? low voltage?
If it's like telephone or computer cable I've used a Tripplette Fox and
Hound to do this. Check it out he

http://www.newark.com/product-detail...alog/5331.html

I wonder whether you could use a small transmitter and detuned AM
pocket radio or two kluged toy AM walkie talkies to do this job.

I've also used my kids play metal detector to trace out larger metal BX
and conduit buried in walls.

Richard