Google Glass
The Google Glass was... an idea. However, it was not executed well at all. Users looked like a Terminator-esque villain with these glasses on, and it wasn't subtle. The glasses used AR technology for use, and there was even a camera installed. Of course, this made the product a privacy issue since it could record anyone at any time without them knowing. Needless to say, the $1,500 glasses didn't take off and flopped.