I came across OpenUPS. It is a UPS for small embedded systems with DC input and output (6-24V, ). It can manage batteries (any chemistry, LIPO? Of course!). It also has software interface for configuring it and control (need to explore this).

But the downside is - it can provide upwards of 6V only. Which mean we still have to use some linear/switching regulator to get the usual 5V the a BEC traditionally was employed for.

Otherwise, looks like a good intelligent compact power management unit. Very useful, I suppose, when we want to build bigger things :)