If you’re in the unusual position of pairing an Android phone with an iPad, or indeed a Mac, and are missing out on the functionality Continuity gives iPhone users, there is a tool which can get you to parity.
Pushbullet is a pretty awesome tool for sharing files, links and notifications, but the Mac and iPad versions don’t support text messages.
Don’t let that put you off though, because the web version does - and it works on both Mac and iPad. Install the Android version to your phone and use the web version to message from your Mac or iPad.
It’s not the full Continuity feature set, but it is the most useful.