In OpenGL you can use CoreGraphics to render into a context and convert that data to a texture. This could be done for each string, but doing so you loose the power of the underlying implementation. If there are libraries that make this easier I am yet to come across them.

Wolfire have written a very good blog post about the issues with text rendering and OpenGL. http://blog.wolfire.com/2013/03/High-quality-text-rendering