Android: Moving from the desktop, where you may have your favourite userscripts set up, to your Android phone, where you're missing all of them, can be painful. TamperMonkey is an Android browser that has full support for userscripts, and allows you to add and manage GreaseMonkey scripts to your Android device.
TamperMonkey is in beta, so keep that in mind when you give it a try. When it works, it works great, but when it doesn't, it can be a bit irritating. Once you have TamperMonkey installed though, as long as you use it to browse the Web, your userscripts will remain in effect. If you want to install a new one, just visit the site where it's hosted and apply it.
Keep in mind that not every userscript will work in TamperMonkey because many of the sites you see while browsing on your mobile phone will be tweaked to mobile pages, or redirect you automatically. It would be nice if TamperMonkey had user agent switching built-in, but as we noted, it's in beta. TamperMonkey is also available for Google Chrome and the Chromium browser on the desktop, and improves GreaseMonkey support in both browsers.