Using iPin for iPhone, Android and BTtogo - YouTube
Samsung Galaxy Gear VR (Explore the world of mobile virtual reality)
Backyard zipline. This would be so cool hooked to the big tree on the hill and it wouldn't need to be hung too high since it would be going right along with the natural slope of the hill.
My favorite treehouse
Manufacturer in China for Apple Accessories! http://nellp64.rurl.me/x05zzb
Graffiti Alphabet Letters
Free! Haruka, Makoto, Rin, Nagisa, and Rei
DIY: origami hearts