In the end, everything will have an app store. Take the Pulse smartpen from Livescribe, for example. The company, whose pen is quite cool (it records what you write and can "remember" things on page, allowing for paper-based calculators and control panels), has just launched an app store for its 2- and 4GB Pulse pens.
The store offers multiple games, tools, and study aids for prices that range from free to about $2. You can download apps here and then upload to your pen.