The NFL is offering a deal for fans to get every preseason game for only $20 through their NFL.com Preseason Live service, which delivers live streaming and on-demand preseason games in their archives. You can watch the games on your computer or tablet devices. The rewind/live service that the NFL offers through NFL.com is definitely worth whatever price that they attach to it.
But there are black out rules to consider.
If you're a Bengals fan within the local market (Cincinnati, Dayton, Columbus, Louisville, Lima), don't be fooled into thinking that you can watch live preseason Bengals games on NFL.com. Nationally televised games are blacked out, no matter what market that you're in. Atlanta hosts the Cincinnati Bengals on August 8, which will be aired nationally on ESPN (you'll definitely see that game live). NFL Game Rewind won't have that game available in the archives until 24 hours after the conclusion of the game.
If the preseason game at Paul Brown Stadium isn't sold out (and usually they are not), then those games will not be shown live on local television. However, the game will be on a three-hour tape delay. If you're in the local market thinking that you'll get the game on Preseason Live, you won't. In fact, neither market for the home and away team will be able to see the game live.
Per the FAQ on NFL.com:
Games that do not sell out will not be available in either teams’ home or away markets for 24 hours after the conclusion of the game.
Now if you're planning to use the service to watch the games at a later date, you'll have the option to watch the archives. Not only for the Bengals, but for every NFL team. If you're a hardcore fantasy football player, this service is only that much better. For the games not being shown live on national television, you have a $20 alternative to watch them on NFL.com Preseason Live.
On the other hand, if you're within the Cincinnati market, there's also a good chance that you won't see any live Bengals games using this service.