WakeMate bursts into flames

Customers of WakeMate, the “first smartphone accessory (wristband) that helps users sleep better,” are being warned not to use the USB charger included with the shipped units after one has bursts into flames. The defective USB charger, reportedly, was made in China.

The company took a quick action by sending to its customers the following safety notice:
Hello WakeMate Customer,

Burning WakeMateWe have just been alerted to a safety issue with our product. The black USB charger bricks that have been included with the product are defective. Do not use them.

The USB chargers were sourced through a Chinese vendor. We paid to have the proper certification and safety tests performed here in the U.S. for the chargers. However, tonight we were informed by a customer of a safety incident with the black USB chargers. Therefore, effective immediately we are recalling ALL USB charger bricks and informing our customers that it is not safe to use these USB chargers to charge your WakeMate.

We will continue to look into the situation but needed to email you immediately to ensure that you stop using and unplug the included Black USB Power Bricks.

We are extremely sorry that we sent a product containing defective components. However, we also want to stress that this issue is with the chargers only, and not with the WakeMate itself. It is still safe to use the included USB cable to charge the WakeMate, and it is safe to wear the WakeMate while sleeping.

I sincerely apologize for this mishap on our part. We are doing everything we can to prevent any further incidents with the USB charger bricks.

If you have any questions do not hesitate to contact me.

Arun Gupta
CEO, Perfect Third Inc.
Here's the video of a WakeMate smoking after bursting into flames uploaded by the victim, Googler Jason Toff:

At a Hacker News thread, the company upon answering questions explained:
yes the batteries are safe. we believe that the chargers are spitting out a noisy electrical signal, which is causing the battery charger IC on the WakeMate to overheat, thus causing the problem. We have only seen any incidence when the unit is plugged into the black USB charger bricks we shipped with. To date we have logged over 20000 hours of sleep on our system, so we're certain that sleeping with the Wakemate is safe, and that the batteries on the WakeMates are safe as well. This is in addition to the testing and certification we had done on the unit as well before we began shipping units.
Via: TechCrunch