phone to phone...unlimited SMS?

I have an idea for an app that requires a lot of data exchange between users of the app. SMS seems like a very simple way to get this done, but is it safe to assume that all smart phone users have unlimited SMS? Otherwise this app won't be very popular due to expensive rates for SMS.

If this is really a bad assumption, can someone tell me what other means I should consider to accomplish this phone to phone communication? Initially I had hoped for an alternative that used data service instead of SMS. But I have read many (so many) forum posts about this sort of thing and have read nothing conclusive.

A bit about my app's requirements:

• Users build up a network of 'friend开发者_开发技巧s' for coordinating among them.
• When one user creates some event on their device, all users in their network should be notified.
• User's can also instant message other users on their network

So, I need a mechanism for getting all of this done. After reading a bunch of tutorials, I can see how I would do this using SMS, just not sure if that's a good idea. Some people have said that this sort of job would require a central server, but I'm not quite sure how exactly that would work. I am not opposed to a solution that involves a server, I just need some help to get me started in the right direction.

Thanks in advance.

Number of SMS does not depend on the phone model it depends on the carrier and country.

How do users "build" their network? When I add a friend I will be notified via sms? How will my friend know that I use this app?

I would suggest using internet and having a "inbox" for every users. Notifications can be sent to this inbox.

Even for plans that include "limitless" SMS, in reality, it is 3000 messages or some other arbitrary limit. And many do not have free SMS at all, each costing maybe 10 cents or more.

There are also technical problems - SMS messages can be delayed for hours and sometimes days until they reach their destination.

Assuming a decent data plan is a much better way to go. What you can do is try to avoid the number of bytes sent. Depending on what your network of apps will do, it is often possible to cram a lot of information into very few bytes if you put your mind to it.

It sounds lika a fun idea for an app. However, as the above posters suggests using sms is probably a bad idea. It is just a too expensive way of exchanging data.

A better way is to develop a back-end for your system. There are many way of doing this, but I would suggest using Google App Engine (http://code.google.com/appengine). Also if your app is aimed for Android version 2.2 I would also take a look the "Cloud To Device Messaging" framework. Using it would keep the data traffic lower since your app would not have to poll for new messages.

Good luck!

This is the best tutorial you can check.

I used it and it is perfectly working......The only problem is that Google let you send 20.000 messages by "PUSH" per day, so if you increase that quota, you have to begin to pay.Android cloud to device(C2DM)