Hantech has an interesting product that allows you to turn any laptop into a tablet PC.
Tablo for laptop (model: TL-01 Series) is an innovative pen input device performing a full tablet function with simple installation. Tablo supports perfect tablet compatibility with Microsoft Windows XP and Vista and provides the finest handwriting, drawing, sketching and illustration with simple touch. This excellent pen mouse allows to maximize its convenience while the following software; Microsoft Windows Live messenger, Microsoft Office, Outlook, Journal Note, and Sticky Note and Adobe Photoshop, Illustrator, PDF, and many more programs where the mouse is normally used. Create and personalize your documents with your own style! Product Features: Monitor Tablet/Digital pen for laptop PC; coverage up to 15.4” wide screen in slim and mini design for mobile user; easy calibration & one-stop installation setting; ultra portability with any laptop PC; powerful & smart mate for presentation & office documentation. System Requirement: CPU: Over 1GHz Pentium compatible, RAM: Over 512 MB, Interface: USB port / CD-ROM driver. Specification: Memory: 170mm-358mm diagonal (15.4 inch), Power source: DC 5V (USB)/LR41 Cell Battery, Technology Ultrasonic and Infrared, Sampling rate: Over 70 Hz, Device standard: HID pen device. The price point is under $100 for US.