I think the post was relevant. I don't mind self-promotion if the thing being promoted has hack value.
[Edit]
Re dsman's comment: "... if every iphone post here attracted comments by all of us who were building an iphone app then HN would be the worse for it"
It depends, IMO, on the nature of the app. Trying to crowdsource weather prediction is a sufficiently interesting hack that I think HN would very much not be the worse for knowing about this. I would only find it objectionable if cryptoz starts promoting in every Galaxy Nexus thread.