I've already spoke some possible future corporate clients, all of them found it great and would like to use it after it's ready.
Sorry for my bad english.
If that's the case, then they should be willing to put their money where their mouth is.
Ask them how much they would be willing to pay for a solution like yours and whether they would be willing to pay (even half of) that upfront. If they don't want to, perhaps they don't really need it or are not your real customers.
There is nothing that will validate your idea better than pre-paying customers.
People saying something is worth the oxygen it took for them to say it. If they put up something of value, then that's worth pursuing.
However, to me it seems like an itch that is very hard to scratch. It all really depends on your execution. Can you really build a product that doesn't annoy the costumers? If so, then it's an idea worth pursuing.
One good way to validate your idea is to look at competitors. Are there any players in this field? Are they making money? Can you provide something better?
Another way might be to perform some sort of "smoke test". Build only the software component that calls and talks to people. Then start calling people you know (without them knowing it's you), and have the service ask them simple questions. Do they hang up instinctively? Do they provide any info? You might even want to call them in person afterwards and ask about the experience, though they might not want to speak to you ever again...
By the way the site has way too much text.
Also the page doesn't work well on browser windows less than 1300px. Just an FYI. Wish you the best!
The biggest ones I'm aware of are AppointmentReminder.org, which is helmed by our very own Patio11, ReminderCall.com, and Inphonite. Beyond that, there are specific appointment reminder applications per given niche (there are like, 3 very large, very expensive ones geared towards health care appointments, for instance).
Do you know of a list of problems which have been solved ad nauseam? It would be useful when coming up with a 'revolutionary' new idea, to quickly check if it is :)
That said, I'm not aware of any such lists, though market research is always encouraged before spending time on development.