Great suggestion on targeting all the sites. Just pushed an update that un-checks every site with the "All Sites" checkbox at the top. I'll look into scraping the Who's Hiring feed next...
For example, the whoishiring user[0] gives convenient access to every post[1] that would interest you.
0 = https://hacker-news.firebaseio.com/v0/user/whoishiring 1 = https://hacker-news.firebaseio.com/v0/item/8681040
Scraping is easy. Trying to figure out the best way to parse/display is hard.