Quote from their website:
"In the process of writing a song, ProChords offers an extensive variety of options as to what chord could be played next, after the sequence of chords you have already chosen during a writing process of a new song."
"ProChords is loaded with more than 9000 different progression patterns extracted from the latest 50 years of rhythmic music. These patterns are used to suggest possible movements at any given point in your song based on the previous sequence of chords."
It includes an "Export to MIDI" function, sending the MIDI file with the progression to your email - to be imported in your favorite DAW.