In the spirit of the question and the hypotheticals raised thereafter, I too am going to get all hypothetical.
DVB-H adapters for both iPads and Android-based tablets are on sale from DStv Mobile, according to their website.
The question then comes down to software. Maybe (here's that hypothetical) it is not possible to reliably get a "normal" tablet to receive push content over DVB-H.
Like with the decoder-based stuff how this is likely to work is by broadcasting the data on a channel. This means the receiver actually needs to be two receivers (so you can watch and "download" at the same time), or it needs to be left plugged into the tablet and the software will need to be able to set the tablet to receive the content during "quiet periods".
This would mean (probably) waking it from sleep at the right moment to receive the data and store it. Maybe Android does allow it: if power plugged in, then if receiver plugged in, then wake and receive; but maybe this would be so error-prone on third-party devices that to be sure it works right they're building their own.