Launching Other Apps within an iPhone Application

Yes it is possible to lunch other apps within an iPhone application, it can be done via URL technique .

Examples of some of the key applications that you can launch via URL are:

Launch Apple Mail
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"mailto://info@iphonedevelopertips.com"]];

Dial a Phone Number (iPhone Only)
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"tel://8004664411"]];

Launch the SMS Application
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"sms:55555"]];

Launching the AppStore
NSURL *appStoreUrl = [NSURL URLWithString:@"http://phobos.apple.com/WebObjects/MZStore.woa/
wa/viewSoftware?id=291586600&mt=8"];
[[UIApplication sharedApplication] openURL:appStoreUrl];