There was a recent Kickstarter selling a 15X lens recently: http://www.kickstarter.com/projects/968523355/micro-phone-le... but this is closer to the work Dr. Aydogan Ozcan has been doing at UCLA. They started 3D printing custom backs for dumbphones years ago. An article from 2009: http://www.nytimes.com/2009/11/08/business/08novel.html
It looks like they've moved to smartphones now: http://dailybruin.com/2013/09/27/ucla-team-invents-microscop... and they can now resolve "a single virus" and nanoparticles down to 90-100nm: http://newsroom.ucla.edu/portal/ucla/ucla-researchers-smartp...