iOS offers a lot more fonts to use dynamically for an application than just the standard web fonts. This site iosfonts.com is a great resource for finding the right font for your application. Talk to your engineer, but any of these fonts listed  should work dynamically in your application. This site also gives you the option to preview fonts in text and numbers with up to 260 facets.  You can also look at what fonts are supported in what version of iOS.