Cashu, for instance, or opendimes, would work just fine, because you're not broadcasting anything to chain necessarily. Both would require trust at that point, as would any other custodial solution. But give them some sort of a seal that can't be broken, and maybe tie in WoT ideas to add in some tamperproofing, and i think given the circumstances you could arrive at something vaguely acceptable.

Still not better than subspace radio, but some science fiction actually tries to be plausible...