Re: GPS in smartphones
My handheld GPS device uses 2 AA cells (rechargable or standard) and lasts over 24 hours. I do long cycle rides and rely on the GPS to get me around - typically 10 or 12 hours. I did the 1000 mile Lands to John O'Groats ride and only used 6 AA cells in total with continuous map location tracking.
OTOH, my smartphone lasts a limited number of hours on a charge and is not sufficiently rugged to use in inclement weather, vibration etc. so it's kept well protected from the elements.
Both have their uses, but if I wanted to have a reliable location for all conditions, it's the dedicated device that wins hands down.
It'll be interesting to see if this low level of battery usage remains when tracking several GPS systems.