A little about me, I m a C/C++/C# fanatic and i do most of my coding in the latter two. I have also done a little bit of Java and VB.

Recently i have come up with a thought of desiging an app which basicaly communicates with Smart Phones.

Currently the Smartphones are dominating the mobile phone market and every 1/3 people carry a smart phone.

I have come up with a thought of designing a an Application with a Database linked. The Database could contain basically anything and eveyrthng (thats not a problem). The problem is that, i want this application to communicate with Smartphones (or any portable devices like tablets or iPads), either via WiFi or maybe a 2.5G - 4G Network.

So my question is, if i were to develop such an application will it be neccesarry to develop Mobile apps for the different types of Smartphones OR is it possible to achieve the above without a Mobile app or knowing the number of the phones?

what would be the most effective and cost efficient way to achieve it?

When i say cost effective, i m mean on the development side of things.

Someone please help me on this. This is not a homework question so there is no due date.