I just joined this forum and I was reading the posts
I love your idea and I think its great to have this kind of products since almost everybody has an I-phone
But why do you limit it to RC cars, boats and planes? hmmm can you make it like a new kind of input that could be interfaced with an arduino or an axon board?
If that is the case you can use it with long range RF modules and you can easily extend the control range and increase the number of applications, especially if you could send back information to the I-phone