It's writing on the users own wall, which they are asking it to do. Therefore it's not unsolicited. It doesn't write on other users' walls, so it's not bulk.
All kidding aside I would hope that it wouldn't be interpreted as spam. It's a novel way to help someone get up in the mornings, and I would like to assume friends would find it humorous.
Now, if the app sent private messages or wrote to the wall of a friend, that could be classified as "spam".