Mac: For all the integration you get between your desktop computer and your smartphone, one place where they don't really communicate is in phone calls. Dialogue is an app that lets you can answer incoming calls on your phone from your computer.
Dialogue uses Bluetooth to communicate between your Mac and your phone. When you get an incoming call, Dialogue rings on your computer, and you can answer the phone from there. Likewise, you can dial out the same way. The app can also record your calls and save them to your computer. It works well, although the built-in speakers and mic on a Mac sound as bad as they do on something like Skype, so a pair of headphone and mic is recommended. Dialogue works on the iPhone, Android and Windows Phone.