This is an incredibly narrow niche you've picked.

I suggest you went at this the wrong way around. Contact companies you believe you can do something for and get THEM to buy in on software that you develop for them...get the customers BEFORE you start programming.

It'll save you a lot of difficulty and frustration.

You can use the Little Unsure technique with receptionists to get into the company. Then repeat it with whoever answers (the receptionist may get it wrong).

http://www.salestactics.org/how-to-get-to-the-decision-maker/