Plan V is a Failsafe Device You Actually Need Right Now
Plan V is a failsafe device you don't need to charge and is so small you can take it everywhere on your keyring. It works much like a car jumper cable. You simply connect a 9 volt battery to the Plan V device and then hook it up to your phone. And since these are the square batteries you find in smoke alarms, they're about as widely available as chocolate bars.