https://blog.azureinfra.com/surface/
https://de.wikipedia.org/wiki/Datei:Surface_table.JPG
https://www.theverge.com/2012/6/19/3096652/microsoft-surface...
"Microsoft Surface PixelSense 'Coffee Table' Hands On"
https://www.youtube.com/watch?v=qh9cOlVFItQ
Granted, this is very hard to search for, when not being around the time it was available, as most results will be about the current tablets marketed as surface.
I consider Microsoft's one great, given its C# and .NET based SDK, instead of yet again C and C++.
Two contact types are provided: Finger – Representing a single touch point, e.g, a finger Glyph – Representing a tangible object
For each contact, you get ID, Position, and Phase. For Glyphs, you also get orientation and touched status, as in the system knows whether the object is being touched or not. There tunable parameters for the tracking system as well.
For event systems (e.g., menus, etc), BoardUIInputModule in provided in place of Unity's default InputSystemUIInputModule.
Please reach out if interested to develop: https://board.fun/pages/developers