How do I find the right person or company to hear my idea for new technology?

I am asking this question on behalf of someone who has an idea for a way to combine existing mobile computing technology with certain software to reach a broad (and growing) market. We think that executives at a company like Apple, Google, HP or Dell might jump on this idea, once it's explained to them; but we have had a hard time finding who would be the right person to hear a "pitch." Company websites sometimes have "Contact Us" links, but they usually don't seem to list the names of people in charge of things like this. Does anybody have an idea where we should direct our efforts?

In an earlier version of this question I included an outline of the idea I'm talking about, but I was advised to delete that question by someone who said it was a good enough idea that someone might try to steal it. I hope I've given you enough to go on! Thanks....