Pajamas can tell you about sleep. This can be done with a special chip and electronic fabric. The company named Nyx Devices brings this sleeping T-shirt, which has nothing to do with a regular T-shirt, but can detect your sleep status and list various data (such as eye movement, heart rate, respiration rate).

It seems that the benefit of this thing is that you can easily view your own status without having to link with various monitoring devices. With the iPhone App and other devices you can even view the data in real time.