If you are on a Wifi and both your mac and iPhone can access it, you can get free ride with controlling Keynote from your iPhone by using: Keymote, which in part uses Telekinesis iPhoneRemote.

Telekinesis actually uses iPhone Safari and Ajax so you need to point iPhone Safari to a specific address (https://192.168.74.104:5010/ by default). You can bookmark it as iPhone shortcut on iPhone desktop though, for easy launching.