iPhone OS 3.0 has recently added support for external iPhone accessory-related apps.
According to iLounge, Apple has added a feature to the iPhone OS, as well as to Made-for-iPod and Works-with-iPhone certified devices, to include automatic download prompts when connecting accessories supported by iPhone apps. If you connect one of these accessories to you iPhone or iPod Touch, an alert box warns you about the missing application and asks for permission to install it.
Griffin's iTrip, an FM transmitter with app support, is the first already-shipping accessory we found that supports this new iPhone OS feature.
The iTrip app is optional. According to Griffin, the app enhances the usefulness of the iTrip by allowing you to control it from your touch screen. Once installed you can:
We're curious to see what future innovations developers will make using this new hardware/app compatibility.