Have you ever considered direct mail or advertising in industry trade journals? Or issuing press releases for those trade journals which are always looking for material to fill their pages? Another thought (cheaper than flying) would be to simply write a few articles for those journals speaking about the general problem of appointment reminding and then having the byline be you. It is something that others are doing. The same article could easily be repurposed for different journals. Once you are "published" you can then do reprints of your articles to DM or hand out at shows if that ends up being an attractive route.
In looking for an example of "card packs" which I have successfully used (in a different business) I came up with this which illustrates the direct mail route:
http://www.behance.net/gallery/Post-Card-Mailer/828394
Cost to spray something like this to 10,000 offices is no big deal. You'd have to repeat a few times to the same people I would imagine to get a desirable response.