There have been similar funds, like the First Trust NASDAQ CEA Smartphone Index Fund (FONE). One source of ideas for new funds are products and services that could be thought of as add-ons and accessories to the above spaces. While there are not enough companies yet, more IPOs of companies like earphone seller Skullcandy (SKUL) could make for a niche fund, although I would be very skeptical of a Pets.com outcome with that sort of granularity.
More fundamentally, another theme to exploit would be the demise of the eurozone, should that happen. Countries like Germany, Finland and Turkey (I believe Turkey would benefit should the euro disappear) would become more attractive and some fund provider could come up with an inverse drachma fund. The one specialty equity ETF that seems to be most clearly missing in my opinion is one tracking publicly traded stock exchanges. In addition to the larger exchanges in the U.S. like NYSE Euronext (NYX) and the Nasdaq (NDAQ), exchanges from Australia, Singapore and Brazil are also publicly traded among many others. Given the sorry state of so many banks this seems like an obvious void.
In the nearer term foreign fixed income and low volatility equity funds will continue to dominate the new listings and investors want more yield and less churn in their equity portfolios. These are powerful end-user demands and fund companies would be wise to continue focusing on this need.