I don't see why you can't build your own, using a PIC should make this easy.
All you need to do is reduce the current to a trickle when the cell voltage starts to drop slightly whcih can be detected using a comparator and a low pass filter.
There is no such thing as prevention, there is only limitation. I can break ANY non error correcting system you can put together. That is why there are so many EMC standards.
Ever hear of jammers? Apparently not. EMP perhaps? Guess that one escaped you as well.
Whether you use manchester coding or not makes very little difference. If you want error free transfer get zmodem protocall. If all you need is a few commands and responses just send CRCs and block acknowledges.