The original Press This spun itself off as a stand-alone plugin, so look there first to recreate its functionality. If that doesn’t suit, try David Shanske’s Post Kinds plugin which incorporates a lot of Press This functionality and extends it quite a bit. You can create bookmarklets with it that work well (including mobile).

Another option is Tom Critchlow and Toby Shorin’s Quotebacks which you might leverage though they won’t necessarily create new posts on your behalf.

If you’ve got some programming experience, you might be able to do something interesting with a set of bookmarklets I just made too.

I think I’ve also shared most of my documented workflow for using Hypothes.is for some of this too, though that may require some work on your behalf.

Another good option is to add Micropub functionality and use some clients like Quill, Omnibear, or others in conjunction with the Post Kinds plugin. I think Quill may also have some useful bookmarklets you can use with it as well.