Lithium Polymer battery packs are widely used in Radio Controlled (RC) airplanes among other things for their charge/weight advantages. These packs typically consist of X series cells and Y parallel cells, and if I'm not mistaken, each parallel segment is ganged across series segments as follows, with taps brought out.
So what I've drawn above as an example is a representation of a 4S3P configuration (4 series, 3 parallel), B+ is the pack positive terminal, where B- is the pack negative terminal, and T1, T2, and T3 are series tap points.
From what I've read you need circuitry to do charge protection to cut off charging voltage when charge is complete (i.e. all cells have reached 4.2V). It's good to have cell balancing circuitry that can selectively bypass series segments to allow the pack to fully charge. And finally it would be nice to have fuel gauge circuitry to monitor / profile the cell / pack state of charge (or equivalently depth of discharge).
There seem to be quite a lot of chips out there for doing "battery management" or "charge management" or "fuel gauge" functions for particular chemistries. What are some tried-and-true techniques? What is the most integrated available solution to this problem? I would think there would be "all-in-one" solutions to "battery management" problem that are equiped to interface with a pack like I've drawn above, why does the landscape seem so varied and federated?