You might have seen some specialized plugins for Autodesk Maya that could interpolate attributes based on distance, basically a proximity reader. One such plugin is Hans Godard’s Radial Basis Function (RBF) Solver. The plugin would describe each pose as a N-dimensional Key and a M-dimensional Value. This means that keys and values can be anything, allowing you to power to interpolate anything.
The thing is, you can totally make a similar system yourself, in Maya, using nodes. Walking us through how, is Bjorn Blaabjerg Sorensen. The Distance and Proximity Reader will read how close an object is to another, and outputs a value from zero to one, which can then drive any attribute. This can be useful for driving blend shapes or other values, easily.