Vat19.com says battery heated slippers are safe because they are battery operated and don't have an electric current running through them. The batteries included usually are removable and rechargeable.
Reviews on brookstone.com give the Volt brand of heated slippers a four out of five rating, and the majority of reviews online are overall positive. With no safety hazard, the only complaints are about sizing and comfort.
With safety as a non-issue, these slippers are also durable enough to wear for quick trips outside due to the thick rubber padding. The outside material of the slippers are water resistant, and the lithium-ion battery is safe inside the wireless remote control.