ADAFRUIT INDUSTRIES 1304, USB Power Switch IC

Adafruit have now created one of the smallest USB LiPo chargers available, so it is perfect to keep in any project box. Simply plug in the gold plated contacts into any USB port and a 3.7V/4.2V lithium polymer/lithium ion rechargeable battery into the JST plug on the other end. There are two LEDs - one red and one green. While charging, the red LED is lit. When the battery is fully charged and ready for use, the green LED turns on. Once you know all this, you are good to go.

5V input via PCB-style USB connector
2-pin JST cable included
100mA charge current, adjustable to 500mA by soldering a jumper closed

USB