Could 8 bit deltas for the x, y, z values gain you anything? If acceleration tends to be straight line then converting to a vector form may gain you something, especially if you then delta encode.
A quite different technique that works well for some types of data is to treat each bit position (or groups of adjacent bits - nibbles for example) in the data as a separate stream and run length encode each "stream". That gives excellent compression for the most significant bits and almost none for the least significant bits, but overall may give substantially better results than general purpose Huffaman type encoding.
True laziness is hard work