I recently had the opportunity to take Trimble Outdoors for Android (using the Nexus One) and an iPhone out in the field. As part of my adventure, I knew a few facts would be true. First, there was no way I was going to get wireless coverage in most places I was going. Second, I had one battery in each phone and no way to charge either. Finally, the days were going to be long and there was no doubt I would drain both batteries before the end of my trip. My solution was a portable battery pack. I ended up trying two different battery packs, a Cinch CP505 and an XPAL Power XP4001. Both battery packs come with an AC charger along with a number of cables and attachments such as USB and iPhone style connectors. Before I left, I fully charged both devices and got on the plane. There really is not much to using either of the devices. All one needs to do is plug in the correct attachment and turn the device on. Each phone happily started charging and I could sleep well at night. In the morning I would find a completely charged device ready to go for the day's adventure. I discovered that with my conservative use of the phones and these two battery packs in hand, I had no issue being out in the middle of nowhere for five days.
Smart phones can be quite power hungry. These portable power packs were really the ticket to having a true "out-of-network" experience. Given all the time I had to walk and think, I also realized these would be quite handy for those times in the airport where I am donating my money to the charging station because I forgot to bring my AC adapter. Prices start around $40-$50 at the low end for these portable power solutions.