Apparently not.
Unlike a lot of apps getting shoveled onto the App Store, Signal is competently coded; performs a useful service, launches quickly, doesn't leak, doesn't crash, and has only a smattering of bugs. Maybe prospective buyers would like to know this, but I have had no reviews so far.
Part of the problem was that Apple mistakenly lists its release date as the day I submitted it to them for testing, instead of the day they actually released it to the public, so I got no time on the front page of the Utilities page. And part is probably too high a price point, maybe $5 is just too much even for niche market apps. Again, I'm flying in the dark here because I've gotten zero feedback.
I also don't know where HDHomerun users hang out. The forums on Silicon Dust seem fairly low volume. Maybe if the HDHomerun were buggier, people would be filling their forums but dang it if the HDHomerun isn't the most reliable gadget on my network. And, I don't want to make commercial announcements on public forums anyway; nobody likes that sort of thing. I'm not a marketing wiz, I am a fairly good Mac coder.
Oh well, I only wasted a couple weeks of spare coding time. I've learned my lessons about targeting larger markets. I learned a thing or two about iPhone development, and hopefully my next post on the subject will be "How I Did Get Rich Via My iPhone App."