Concerns about the stability of lithium batteries is nothing new (see exploding laptop toward the middle of this video). Even though battery technology has improved, and problems are rare, when they do occur they can be very serious; e.g., “An iPhone spontaneously combusts on an Australian Flight” by Mike Dunn, 28 Nov 2011, digitaltrends.com.
Suggestion: When powered or being recharged and not actively watched, all devices that contain lithium batteries (which includes most personal computers, cell phones, and other PDAs) should be isolated from your body; e.g. store small devices within a flameproof leather pouch. Devices being recharged should be located away from combustibles.