Contrary to Popgadget's headline, the Choc-U-Lator does not make math delicious. It is, however, the most sadistic stocking stuffer ever. Imagine a child unwrapping what looks to be a chocolate bar only to find a calculator that looks like chocolate. They'd be scarred for life, which is totally hilarious.
The Choc-U-Lator does have the "sweet smell" of chocolate, according to the Japanese product page. But aside from the looks and the smell, there's nothing chocolate about it. To top it off, it only performs extremely basic functions.
So let's recap: Not real chocolate. Not exactly an upgrade for a TI-89. Verdict: not worth $4. You're better off buying a real candy bar and stealing a cheap-o calculator from the bank.