Got some numbers for the SoShine BeOne 4xAAA charger from DealExtreme. Starting with a fully charged n800 + Soshine using 4xAAA (SoShine 900mah) it played continuous video for 6 hours and 6 minutes.

Performance Comparision:

Tekkeon MP1550 + 4xAA (2000mah eneloop): 8 hours 56 minutes
SoShine BeOne + 4xAAA (900mah Soshine): 6 hours 6 minutes

Price Comparison

Tekkeon MP1550: $25 + ship + 4xeneloop => ~$45
SoShine BeOne: $9 + 4xAAA => ~$15

I wouldn't rule out these SoShine chargers - the price/performance is probably good for most peoples needs (i.e. medium length flight), the AAAs are good for iGo keyboards as well, and they feel slightly more robust than the Tekkeon but they are definitely not as cool looking, and have a fiddly switch. They also lack a voltage regulator but after reading recent threads of people frying their Cradlepoint routers on EvdoForums when using larger Tekkeon units I have my doubts about how effective these are.