Some background: when you want to use Camera in Android (as an application), you must setup it by specifying some constants. You must specify resolution, framerate, encoder options. This data usually used by internal CPU (DSP) for producing encoded stream in your hardware, you can't programm it. So, you must setup some options and get encoded stream for this options.
So, sorry, you can't use multiple applications at same time. At least, with different options (framerate).
But you can do workaround: you can decode HD stream, scaledown, encode again and stream to any service you want. This is very heavy task for CPU (in which apps works), so even if your phone can do it, it will very fast drain battery. Better way if to stream HD to some PC or server, recode it and re-stream to any other service.