One option would be to use AppleScript:
$ osascript -e 'id of app "Finder"' com.apple.finder
You could also do something like this:
$ bundle=$(mdfind -onlyin / kMDItemKind==Application | grep -i "/Finder.app$" | head -1) $ defaults read "$bundle/Contents/Info" CFBundleIdentifier com.apple.finder
Both of these are fairly slow (about 0.05-0.2s on my Air) though. Are there any faster or less hacky options?