iPhone 4 and 3GS. The iPhone 3G didn't have a hardware video encoder, if I recall correctly, so we disabled broadcasting on it and anything lower (though viewing works just fine!).

I think we also tested on the latest iPod Touch and found everything worked. I'd have to check my notes to be certain though (sorry, not in front of my work laptop, looking after my 1-month-old daughter right now!).

What H.264 encoding is used (profile, level)?

Would definitely have to check my notes for this. I'll follow up.

What bitrate do you aim for? Is it different for 3G vs 802.11g/n?

The OS gives us a limited degree of control on this one. We get to specify the bitrate as "high", "medium" or "low" and it appears to be completely undocumented what each one maps to, if they're the same for each device, etc. In practice it looks like "low" is always around 80-120kbps, "medium" is about 800kbps-1.5mbps and "high" is somewhere north of 4mbps. We use "low" and "medium" depending on how much actual network bandwidth we think is available.

What framerate/resolution?

Resolution depends on the camera - we don't modify it away from the native resolution. So far, either 480x360 or 192x144 depending on device and selected camera.

Same is basically true for framerate. So far every camera I've tested has given us 26fps.

The iPhone 4's camera is 1280 × 720 though . . .?

Would definitely have to check my notes for this. I'll follow up.

Baseline profile, 1.3.