In addition, I think it's wise to wait with approaching investors (be it angels or VC's) until you have some actual stuff to show them. People (and especially investors) are hard to get enthousiastic with only an idea, whereas a pilot/demo can really trigger them to see the success in your startup.
A friend of mine did the same thing and simpy used screenshots of a static HTML-version of their web-app to show the VC's, and even that was enough to get them to invest.