This small module incorporates everything needed for the TI BQ25703A programmable regulator. This is the same regulator I use in LiPow.

http://www.ti.com/product/BQ25703A

Some key features

• Charge 1 to 4 Cell Batteries From Wide Range of Input Sources
• 3.5V to 24V Input Operating Voltage
• I2C Programmable
• Output 4.48V to 20.8V in OTG Mode Compatible With USB PD Output 1.024V to 19.2V in Battery Charging Mode
• Output Current Limit up to 6.35A
• Thermal Shutdown Input, System, Battery Overvoltage Protection, MOSFET Inductor Overcurrent Protection
• Charge Any Battery Chemistry: Li+, LiFePO4, NiCd, NiMH, Lead Acid
• Currently, I have a driver in LiPow for this regulator. I will be improving on it and making it available as its own project and I would like to make an Arduino Library as well.