If you have a Macintosh with more than one version of InDesign installed, and you want to avoid accidentally resaving a CS2 document in CS3 format – then Lightning Brain InDesignProxy is for you. Click here for more info.
Version 1.0.6 adds support for more file name extensions: .indd, .indt, .incd, .incx, .icml
But more important, when you assign a file name extension to InDesignProxy, version 1.0.6 will now add proper Adobe InDesign icons to any documents it manages. So your InDesign CS, CS2 or CS3 files will always carry the correct document icon, even if you have CS4 installed.
More info here…