Autonomous project power supplies

I have plans for a few autonomous projects, with differing power requirements, some which will fall into the wearable category.
While I know a little about electronics (V=IR springs to mind) I know enough to understand I am out of my depth. I am a software guy.
So my requirements are:
All will be powered by LiPo batteries, the wearables probably by a 1s LiPo others by a 3S LiPo
The Arduino boards I will be using vary from the Mega to the Nano
These projects will all involve the use of components which work at 5v and 3v servos, motor controllers, sensors such as the MPU 6050 and other I2C devices, and of course lots of LEDs, some powered directly from the Arduino, others by LED controllers.
Input voltage monitoring or at least low voltage shutdown should be available.
LiPo charging via USB would be nice, but probably only makes sense for the 1S LiPos.
So all I ask is a power regulator which can take a 2S or 3S as input. Provide 5v for an arduino board and 3v for sensors plus any 5v to 3v adjustments. (I have no idea what happens if you connect the I2C logic lines from a 5V arduino to a 3V MPU 6050 with seperate Vcc connections)
This should also be able of supplying voltage to LEDs motor controllers and servos at 5V which would exceed the power supply capabilities of the Arduino board.
Also a much smaller device suitable for wearables, with similar specifications but powered by a 1S Lipo.
I hope this makes sense to someone out there who can help.
And I do realise that this is a very broad spectrum.

Take a look at pololu,com, they have a bunch of switching regulators that will support various current amount.
For I2C, pullup to 3.3V, then both 3.3V and 5V devices can be connected. Output of devices are open drain, so all they can do is pull the bus low, the pullup resistor brings it back high.

Thank you for your suggestions, most helpful.
Of course if the smoke detectors go off when I fire up the prototype I may be back :slight_smile: