Let us not forget the reason electronic machines were pushed, was that the paper ballot's in florida were, apparently, too complex for everyone to figure out consistently, and thus the push for a touch screen based system. At any rate, I'm not a crusader for electronic voting machines. A simple paper ballot works. It is also very difficult to introduce fraud in a massive scale into such a system.
You can, if you want, consider my post a, if your going to go electronic then you need to make sure you do it carefully, and in a well thought and publically reviewed manner. You point out a fairly unlikely way to monitor an election and that is to try to monitor the RF generated.
Basically, with any design that you want to be publically trusted, I see no reason that you could not lease a copy of the the system to people in the public for review by independent groups. The hardware does need to be kept track of though, and the official seals should be removed from it. You should also probably deface the plastic with a dremel or something and etch in something like "not valid for an actual election." to any machines leased out for review.
The best security is usually involves layers. Sometimes little things enhance security and sometimes big things. Careful design and appropriate shielding can likely make picking up anything via the recording of radio frequency emissions next to impossible. The careful use of cryptography can make the running of code that was not signed by a central authority very difficult. The allowance of independent review of the systems can expose problems which can then be fixed in the next version of the system. [This includes the issue of making sure the voter order cannot be determined by the paper trail that someone else mentioned.]
All in all though, I think most people can agree, that if your going to trust the future of our country to it, you need to do far better than they have done with what is available now. Just the use of printers, and at least spot checking the results by hand of any places where the exit polling differs from what is reported signficantly brings us a long way, but I'm of the opinion that if your going to go electronic you should do it right, such that at least the majority of the experts in the area agree that it is done right. We are certainly not there yet, but hopefully we will move in that direction, since I rather doubt we will go back to a pure non electronic paper only ballot anytime soon.
Finally, I encourage review of the rest of the voting process. It does little good to have the results of one machine tabulated correctly, if somehow that result is not correctly and verifiably added to the tally.