Backpacks could be segmented
Sleep apnea could be solved by side sleeping
Purses, bags, backpacks, wallets, jackets, clothes etc. could charge phones
"Forest backpacks" could prevent illegal logging / encourage sustainable forestry
DayOne waterbags could be used for disasters, survival, and camping
Cats could travel in backpacks
Backpacks could be bulletproof or have bulletproof vests
Backpacks could float