If you want to add an inexpensive signal device to your kit- I totally recommend using a CD- Grab any old America Online CD, or even better a business card cd that some companies use as promos. They are light, reflective and if they bust just toss and replace-

To use, hold in one hand take your other hand and hold up your fingers in the peace sign at arm's length, then move your hand so as to position the plane/ boat you are signaling is between your fingers. Then with your other hand take the cd looking through the center hole flash the sun's reflection on your fingers as you keep the target between your peace sign. (of course this works with any reflective device to target)