If you want to view Packet Radio transmissions on your iPhone connect it to a radio (or even set it next to the radio's speaker), tune in a Packet frequency, and watch the decodes. However, only 1200 frequency baud packet is decoded.
You are also able to see bad CRC packets, just turn on the Bad CRC Packets switch. You can also see information frames (packets), and not display control packets; to do that turn on the Info Packets ON switch.
To use this app, feed the audio output from your radio into the iPhone. You can do this with the Camera Connection Kit. Plug a USB input sound device into the iPhone, and use a patch cable between it and the radio's audio output.

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See Also: A Brief Intro to the Massive Wireless Networking Business