Draq Queen works for us. I can't imagine the alarm blaring over the the big stereo as the phone alone is quite loud. I hook the phone up to an external battery as the app will kill the charge extremely fast. Sleeping in the bow v-berth, I set the alarm for two boat lengths at anchor and one boat length on the mooring. Most of the alarms have been for GPS accuracy. I still wake up, but I do not have to pop up like a prairie dog through my hatch to check our position.

Cheers, RickG