Is there an Android app that pressing on words translates them?
I found the Pleco app manages to do this task using the (free) option Screen Reader:

For example, browsing online in a website:

If we press on the button
, the app recognizes the characters and pressing on any character gives the pinyin and the translation:

You can even listen to the selected character or the whole text with the corresponding buttons: .
From my testings, this function works fine in Whatsapp, Instagram and Facebook chat. But it does not work in Wechat or Facebook posts.