Practical solution: Hotspot along with image processing to convert the hotspot location into an exact location on the bat and convert it into a "contact map" similar to "pitch map."
Impractical solution (but more accurate): Cover the bat with a thin film which contains a grid of pressure sensors (just like a touch screen phone) which then interfaces with bluetooth (or similar technology) and transmits the data to a computer which processes the data and gives an exact location. This is extremely impractical because it includes putting a "tape" on the batting side and have a battery on the bat to do wireless transmission. I only gave this solution because the question said to exclude hotspot, which is the most practical solution I can think of.
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