When you cold-email or cold-call, you need to expect sometimes a return rate of 1% or less. If you've sent out just over 100 emails, you should expect maybe one person to possibly get back to you. You could consider me that "hit," since I hire sound designers for software projects, if you wanna argue statistics. :-p
Apps are the Hot Thing, but remember there are a LOT of other platforms out there...and that games aren't the only pieces of software that need sonifying. Heck, with HTML5, I'd argue that the opportunities for sonified software experiences are still increasing.
I gotta say that the best solution in my experience here is to network. Spend more time here and online, start a blog, take from and give back to the companies, communities, and groups you want to collaborate with, attend conferences...building personal connections will deliver a far higher percentage of potential job leads than reaching out cold (but there's still a place for that, too).
For games, check out IGDA as Dave suggested, but also GANG, for other practitioners in that field. Hit up the design agencies you'd want to work with: Think about if there are local shops that do rich-media flash work, that kind of thing. Attend meetings of groups of those people, be it the Apple Worldwide Developers Conference or local iOS coder's groups or the Broadcast Designers Association or the Interaction Designers Association or one of the several visual effects society. If there's a cocktail hour or a lecture for any such group, go! It's not all icky-gross schmoozing...it's about building relationships. If you meet someone from an influential shop or studio who's a total $&*#$#, then you probably would never want to do business, and lesson learned!
It's also important to not just show off your work, but that you're actually a Human that can communicate, laugh, and meaningfully collaborate smoothly with others. That matters more than raw talent in many, many cases.