This is old idea base from the old fashion clothes pin. I reappropriated it to clamp beach towels and pin it down on the sand, hence "the pin". This should keep the beach towel from flying off. There is a compression sleeve for extra grip.
#68 Portable Bluetooth-Dolby Surround System -Weatherproof-Perfect for the Beach
This is a 4 piece speaker system. This should be heavy enough to hold down a towel in moderate wind conditions. Speakers are approximately 150mm length, can easily be pakaged. Target market - High Tech/Gadget Freaks/Trendy Gals with Smartphones.