I've been working alot with software version numbers lately (did I mention I have a job now?) and one of the tools I developed, that didn't eventually get implemented was a little utility that could fetch the Info.plist info from a bundle based on it's bundle id, for example:
$ versioneer org.videolan.vlc
* org.videolan.vlc: 0.8.6b
Since it can also work with the plists from a user's homedir, you can also do bigger lookups:
$ versioneer com.panic
* com.panic.Audion: n/a
* com.panic.Coda: 1.0.3
* com.panic.Stattoo: n/a
* com.panic.Transmit3: 3.5.6, Copyright © 1997-2007 Panic, Inc.
* com.panic.Unison: 1.7.9, Copyright © 2003-2006 Panic, Inc.
And finally I added the option for reading a specific bundle, as in:
$ versioneer /Library/QuickTime/Perian.component/
* 0.5
The source is here, if anyone needs it.