With Handwriting Calculator from Nokia Labs you can doing math easily, this application has handwriting recognition technology which allow you to calculate handwritten math expressions with a touch-screen Nokia device and with a Windows PC. The application is compatible with S60 (Nokia 5800 XpressMusic and should work on all Nokia touch devices based on S60 5th Edition), Maemo (tested on Nokia N800 and N810, and should work on all Nokia internet tablet devices with OS2008 software), and Windows PC

Download it through links below

installer for S60 (e.g. Nokia 5800 XpressMusic)
Download

Installer for Maemo (e.g. Nokia N800, N810)
Download

Installer for Windows PC
Download