I just used the Text sketch feature to extrude a text on a flat surface, but this doesn't seem to work, or be that straightforward, for a cylindrical or spherical surface.
The text will have to be created on a sketch plane (flat), but can be extruded to any shape surface as long as you don't create a disjoint body. You may need to create a underlying band to "catch" all the characters.
Once you have the text extruded, you can cut any shape you wish out of it to "remove" the flatness from the sketch plane it was created on.
I have created a simple part demonstrating how to do this. You will need to use the offset from surface end condition and start on the tangent point of the surface and extrude away from the surface.
Thanks Tim, Scott and Bill (will email tnx), I've already seen two solutions. It's always good to have alternatives; one may be more appropriate than another depending on the situation.