I am currently working on capturing signals into the iPhone. I want to develop an application to show digital signals. For this I have a device which samples signals from circuits and converts it into binary data and gives its output via a usb interface(I can connect this usb output to a laptop's usb port). I want to know how can I synchronize this usb output and capture it on the iPhone? Is it possible for the iPhone to recognize any such external device.
The current SDK doesn't allow you to handle any communications directly on the USB port, you are limited to normal network connections through Wifi/3G or Bluetooth. You could make the laptop relay this information to the iPhone, but since you already have the laptop, you could use it to store the information and serve it to the iPhone as a simple client that queries a remote database.
Another possibility would be to enter the iPhone hardware program which allows you to design hardware compatible with iPods/iPhones and make it connect it directly to the device you have. This would allow the iPhone/iPod to read/capture directly in real time the data. However, I don't know about the details of the hardware program, nor how much it costs or how to make such a device.