This is inspired in Helghe Mathees pixel particles... I've built it with factory ICE nodes though (as oposed to custom C++ ICE Nodes).
It works by converting points in UV Coordinates to Barycentric Coordinates and back to XYZ Coordinates :D
Actual function can be found in here:
The thing is slow (it is actually 18x faster then my first proof of concept) but can perform ok in low poly objects. Other limitations include only working with triangulated objects :p
Thanks to Helghe and Eugenio Miolo for explaining me a bunch of stuff needed to do this.