I was thinking that an important detail regarding whatever emergency flotation option you choose is to consider how you will attach it to yourself. If you must hug/hold on to the flotation it will sap more strength from you quicker. Consider some type of tether or strap so that you don't have to exert so much strength to hold on to it.

I definitely agree with you about the compass. Brunton makes some good little accessory compasses, including pin-on and watchband models. I wear their watchband compass every day and it has held up well.