There are many different options out there for mixing your Boxcast video. The below options cover only a small fraction of them. Feel free to make a choice that suits your broadcast needs.
While we will certainly help you if you run into issues when implementing a mixer but your best bet will always be to contact the actual product manufacturer themselves as they will have a far better idea of the limitations and uses of their product.
BoinxTV ($499) - Mac only
VMix (Free - $1200) - PC ONLY
Note: You will need a video capture card to bring your camera signal into the computer. 1 capture card per camera.
Roland V-1HD - ($995) Highly portable unit with enough features to satisfy a standard broadcaster.
BlackMagic ATEM ($995 - $1600) More of a rack mounted system but great bang for the buck.
Tricaster (~$6,000) The cadillac of mixing equipment. High end quality and features.
mixing, mixer, switch, production