Similar flavors to caffeine? My wife and I enjoy drip coffee, french pressed coffee, espresso, black tea, green tea, and just about anything caffeinated.

However, my wife wants to avoid caffeine due to its physiological effects.
Unfortunately, in her words, decaf espresso "tastes horrible," and I agree.  I have similar feelings against decaf black tea.

Is there anything with a bitter flavor similar to caffeine that could add some of the punch back to decaffeinated coffee or tea?
Caffeine is definitely bitter. About the only thing I know of that can add bitterness or that strong flavor to coffee is roasted chicory. It's a key ingredient in French Market coffee blends, and it makes them taste pretty darn strong, even though they have less caffeine.

You can get roasted chicory by itself at some supermarkets so you can add it to your decaf coffee, but it may be hard to come by in your area. If you can't find that, see if there's a decaf French Market blend. That'll have chicory and may give you back the bitterness you crave.

I think you're probably out of luck on the tea, though. You might just cut well back on the tea and drink regular tea once in a while. A jolt of caffeine now and again won't kill you, and life's too short to drink tasteless tea.