I know someone who know's someone, who's uncle's brother's cousin has had these
and here are my thoughts on how well they work:
Descramblers: I have not seen them for Digital Cable yet. Some advertise "digital" converters, but they have a digital readout and work with analog cable, as opposed to working with digital cable. I may be a few months outdated though.
Analog descramblers replace your existing cable box, and usually allow you to receive all channels offered by your cable company, including pay channels and pay-per view channels. Usually the only way the cable company will know you have one is if you invite them into your house and they see it. Supposedly, some cable companies have equipment that allows them to do a "drive by" and detect that you are using a picking up an illegal signal. I have never actually known anybody who has ever experienced this. It seems unlikely that it would work, as they would have to drive by as you were "stealing" a signal, and most people are at work when the cable companies are at work, at home stealing cable after work.
Cable companies also generally don't send signals to "zap" them, at least not in the Pacific Northwest. I do know that they commonly send signals to zap the cards for satellite TV, but not analog cable.
Descramblers can cost as much as $500. While it is not illegal to sell or buy one, it is illegal to use one to steal cable or to use it without notifying your cable company.
Filters for Digital Cable: These allow you to watch pay-per view events (movies, sporting events), but not "pay" channels (showtime, HBO, etc.).
The filter hooks to the "input" connection at the back of the digital cable box (the box supplied by your cable company), and then the cable from the wall hooks into the filter. It takes longer to actually swing the cable box around and unhook the cable and then it does to install the filter). The process of ordering a PPV movie is exactly the same whether you have a filter or not (except the paying part
).
In simplified terms, the cable company regularly (probably every day or two) broadcasts a signal to your cable box asking it if you have watched a PPV movie. If you have, the box transmits back which movie you watched (date, time, etc.) , and then you get charged for it on your bill. If you haven't, then I believe the box doesn't repond back ( or responds back that nothing was viewed).
If you have a filter attached, when the box replies "here's the movie I watched", the filter instead replies back "no movie watched", and you never get charged.
Filters usually cost less than $25 ( I have of them being less than $10), and may or may not work with your box. You test them by hooking one up and ordering a movie. Check back in a week or two with the cable company and see if you were charged. If you were, it doesn't work, if you weren't, then it does.
Now for the question you are all going to ask:
I don't know how long the box stores the movies you watched in memory. I can't imagine the memory being that large.
So if you unhook the filter, the box might transmit the movies you watched back to the cable company. Most filter instructions probably recommend not unhooking the filter. I don't know what you do if you have to have a repairman come, since you obviously don't want him to see the filter.
Hope that helps!