1. Open the app.
2. Add a new group
3. Add contacts from the address book to the app or add them manually.
4. Press "Send SMS to group"-button from the group and it opens the in-app SMS-windows with all the contacts added to the "to"-list from the group.
Next time a person wants to SMS this group, just open the app, select group and press "Send SMS to group".
Very easy app, should be able to code in short time.
Here's the function that allows to send to multiple numbers.
Ps. the at's are removed from strings because of Scriptlance policy:
-(IBAction) sendInAppSMS:(id) sender
MFMessageComposeViewController *controller = [[[MFMessageComposeViewController alloc] init] autorelease];
[url removed, login to view] = "Hello from Daniel";
[url removed, login to view] = [NSArray arrayWithObjects:"12345678", "87654321", nil];
[url removed, login to view] = self;
[self presentModalViewController:controller animated:YES];