Launch app periodically with Automator
You can also use AppleScript instead (/Applications/Utilities/AppleScript\ Editor.app/).

The following script starts the Terminal.app every seven seconds:

on idle
    tell application "System Events"
        tell application "Terminal"
            run
        end tell
        return 7
    end tell
end idle


Save this script as an application and let it "stay open after run handler".