Quite a fun little device that works with most tablets (plugs into headphone jack). Mixture learning games in the app which can help child's writing skills etc. Is £5.49 on Amazon.

Easily worth a quid - the original £9.99 is maybe a bit steep though...

Here's their blurb:
Appen is the revolutionary pen for colouring, drawing, learning and playing.
Key stage educational values teaching your children how to write letters and count in a fun way.
Pressure Sensitivity--the harder you press the pen down on the device, the thicker the line.
No batteries required--Immediate fun: download free app for plug 'n' play.
Compatible with ios & selection of android devices.
Easy to use: can connect to smart devices via the headphone audio jack connection.
Capacity to track child's learning progress & share with friends & family, updates sent to social media & or email account.