If I had a pool I would totally try this out. Put a glow stick in a balloon for pool lanterns. Pool party on a Summer night! I think this could work pinned up on the fence of a backyard without a pool, too, so really great idea for any outdoor BBQ/party!
The DIY Romantic Star Projector from Infmetry looks almost too good to be true. For those of us living within city limits, this is the closest we can come to a starry night without having to travel to the country side. And yeah, it is pretty romantic.
Photo Booth for reception - LOVE! We used a red round frame for reception photos at a wedding here at our farm. the photographer edited for black and white photos with only the red frame in color. Definitely worth a try.
Set of 3 Floating LED Pool Speakers. Simply toss the waterproof speakers into the pool and start the music, transmits wirelessly via from a single bass station. When not in the pool, the speaker work equally well on dry ground.