I used DejaVu for a math symbols app, and it covered every symbol required http://mathsymbols.net/ http://mathsymbols.net/ The main problem was Apple products,

I used DejaVu for a math symbols app, and it covered every symbol required http://mathsymbols.net/ http://mathsymbols.net/ The main problem was Apple products, surprisingly. It's crazy the iPad and iPhone don't have better Unicode support!