Nice one!
Here is what I use. They have it at homedepot Canada stores for $10. The probe is underneath I opened it and soldered old headearphone wires at the contact so I can place the wire where leak will likely be. It uses a 9v battery. I connected 9v power adapter so I don't have to worry about changing battery. I just test the end probes once in a while for peace of mind.
They have a wifi version of these things now. That might be a splurge for me to spend.
http://m.homedepot.com/p/Re-Useable-...WD21/204116885