Recent reports suggest that there may be an overheating/fire hazard from a small number of Apple iPod Nano devices. There have been cases in which overheating, apparently of the lithium-ion battery, has caused burns to wearers, devices have caught fire will in pockets, in use and unattended.
One incident occurred on a cruise ship, another in a parked car.
1) As with all devices powered by lithium-ion batteries, keep them away from flammable materials such as paper and clothing.
2) Do not left them laying on a bunk where they may set fire to bedding material
3) Do not leave them in, or let the fall into enclosed situations such as between cushions which may encourage overheating and provide fuel for any fire that may occur.