Samsung DeX is a feature on the S8/S8+, Note8, and S9+/S9+ that allows you to dock your phone and use it as a basic desktop computer. An updated DeX Pad launched alongside the Galaxy S9 and S9+, and it has already gone on sale once. Now it's down to half its original price - just $49.99.
The DeX Pad has two USB 3.0 Type-A ports, an HDMI output, and a USB Type-C port for charging. If you don't have a USB keyboard and mouse handy, you can use your phone as a trackpad or touch keyboard. There's also a fan, so your phone doesn't get too toasty.