Here’s my first attempt at an Alfred 2 workflow: Compare Finder Items in Kaleidoscope.
It compares two selected Finder items with Kaleidoscope. E.g. select two files and hit your hotkey (I used ⇧⌘K) and the files open in Kaleidoscope. Same for folders as Kaleidoscope 2 can compare folders.
It calls a shell script that runs an Automator workflow. It does some simple checks. Errors are logged to system.log with logger(), and a notification is sent to Notification Center.
Small Update: to improve syslog output.
Updated workflow: Compare Finder Items in Kaleidoscope.