Attract attention to yourself, from a humble Whistle, to the more advanced Personel Locating Beacon, we can make it happen.
A standard magnetic compass is a good back up to a GPS. There's no point in replicating, just use your diving compass.
Satellite based personal distress, location and tracking beacons. In the event of an emergency these provide the best possible chance of being found. They are very much a last resort and should only be used in situations of EMERGANCY. Unwarranted activation can lead to prosecution.
They're not a distress signal but will aid your location when used in conjunction with other signals or devices also very handy at night. A good quality depth rated dive strobe light/torches are a necessary for divers, but kayak fisherman can also benefit from the strength, durability and waterproof qualities in such a wet environment.