You don't really have to send the entire video feed from the camera, only the part your looking at. That way, most of the "software" is running remotely, and you also don't have a mechanical component to worry about.
Burners are an effective defense against single-phone-number taps.
But in an era of dragnet surveillance and meta-data analysis [1] they're not very useful.
Unless you're calling varying phones, at varying places, from varying places, at varying times, all with no discernible pattern or schedule -- it would be easy enough for them to identify a network of burners and determine which ones belong to which individuals on the network based on that meta-data. And if anyone in the network carried or used a 'real' phone alongside the burner, it would only get easier.
And you can Google search on the news wires to see how well people do at this game, even when they know their lives are literally on the line and thus devote a significant portion of their effort toward it.
[1] Done well-enough to be confident-enough to lob hellfire missiles at SIM cards in not-quite-friendly countries...
Maybe if you speak in code the whole time, and never reveal the identities of both of you. The contents of the conversation will not be secure, so you have to assume they are hearing it, but don't understand what you're talking about. That may be a little difficult.
