Don't buy the Energizer NiMH, get some Sanyo eneloop. They are some of the best low self discharge NiMH cells. I do use eneloop for AA and AAA form factor applications, but for my front light I've switched to a dynamo hub and a Lumotec IQ Cyo, which works great even for 300 km brevets.

For my smart phone I currently use a 18650 cell based USB pack for backup power (this covers 20 hour brevets too). I use relatively inexpensive Trustfire 2500 mAh protected cells, which have worked well for me so far. I'd stay away from Ultrafire.