Quipeace released a calculator for Nintendo DS.

Quote:

Inspired by the handwriting calculator from nokia labs, I started working on this, never knowing that it would turn out much and much harder than I first expected.

Features:
Basic math operations: (+, -, *, /, ^)
Multi-digit support.
Handwriting recognition (now using graffiti).

http://forum.palib.info/index.php?topic=7850.0