Do you have any paying customers? If no, then why dont you get some? You could tell them that the app will be out in the next __ weeks and if they sign up now, they can get a lifetime discount of 30%. This way, you will be able to bankroll though your customers and use this money for your development.

In today's environment, even if you approach investors, they will tell you to come back after you have seen some traction.

As far as your development costs are concerned, I suggest you find some good offshore development freelancers. There are very good developers I know who can help you out.

Do let me know if you need any inputs on this.

Vivek