Wetpixel member Alessio has posted a list of leak and moisture alarms in his search to find one that can be retrofitted into his Sea & Sea DX-D70 underwater housing. If you have a third-party leak alarm installed in your housing, head on over to the thread and add to the list!
Leak alarms provide inexpensive, easy insurance against minor floods. If you have an expensive camera inside an underwater housing, you should definitely have some sort of leak alarm installed. It’s definitely saved me, in the past.