One of my favourite clients recently asked me how he could sound more energetic, alert, dynamic (and increase his voice flucutation) while on the phone, especially on long (or boring) conference calls. My answer? Get a simple balance board. This will keep your mind from wandering since you have to concentrate on the present moment (to stay upright!) and will prevent any hint of boredom from showing in your voice.
My current balance board is from Reebok: http://www.amazon.com/Reebok-05-55101-Balance-Board/dp/B003PAZ7B4