Mac: A lot of apps secretly check in with the mothership behind the scenes without asking your permission. If you'd prefer they didn't, Radio Silence can solve your problem hassle-free.
The basic idea behind Radio Silence is to completely prevent a specific application (or two, or three, or more) from using your computer's connection to the internet. Think of it like an internet blacklist for your apps. You just add an application to that list and it will not be able to send or receive any data. If you were to put your web browser on there, for example, it would pretty much render it useless.
So why might you want to do this? A lot of apps send data back to the companies that made them without ever telling you. Generally this data isn't anything you'd care about -- it's just data to check for a legitimate serial number or send anonymous system information. That said, some apps may send back usage statistics or other things you may prefer to keep private. Whatever the case may be, you don't have to worry about it if you put them on Radio Silence's list.
Many of you have probably heard of a similar app called Little Snitch, which essentially does the same thing. While Little Snitch is great, it costs $US30 and is a bit more complex. It also has a lot of popups to alert you when apps are trying to phone home. Radio Silence takes a more hands-off approach and only costs $US9. If you don't need a bunch of features and just want the job done hassle-free, it's a great alternative.