Adapted from 'Combined Points for Trello' extension (see https://chrome.google.com/webstore/detail/points-for-trello-combine)
This extension adds Reach, Impact and Effort priority badges to trello cards.
The values are added by including [R:1] [I:1] [E:1] in the card title.
It also adds a "Show Easy" button to the top of the board which will highlight the 3 cards with the lowest effort assigned that don't already have members attached.
Note: Still a work in progress, cards will take up to 5 seconds to update when tags are changed.