I got to meet Jack once, and had a great conversation with him. He was interested in knowing what draws someone halfway around the world to see a rock performance. He's had a huge impact on U2 over the years, and I think he's going to be missed greatly.
We all know there's a song called "North Star" bubbling under. Bono has refered to it as a tribute to Johnny Cash in the past. But I wonder if some subtle lyric changes hasn't left it more as a tribute to Heaslip, after the thank you in Songs of Innocence referring to him as U2's North Star. For those that don't know the song, it was performed live a few times on the 360 tour live in Europe in 2010, and appeared in the third "Transformers" film. The original plan was to release the album in 2011 before the tour resumed, and "North Star" would have been a single ala "Elevation" in Tomb Raider. When the album wasn't ready the rest of the plans didn't go through either, but "North Star" still ended up in the movie...but a full version has never been released.
Might be waiting for "Songs of Experience", or the final "Songs of Ascent" if either of those happen now.