This gadget for an iphone is reviewed here (http://gizmodo.com/5865625/compass-eye-im-sailing-away ) by Gizmodo for sailing, ...  but not all are fans. This comment from Jack Matt brought a smile ''yeah but how easy is it to take bearings from your mounted compass when the boat's rocking or you're at a optimal tilt. You need a good hand compass. Question is if you're taking bearings you 

Sailing Apps -- Stocking Stuffers
They're mostly inexpensive, and sailors with smart phones or other devices will find many apps useful, fun, or both. It's great to have navigation, tide and current ... links to a short review-blurb by Thomas Lochaas