iPad Stylus - Cosmonaut $25 - a bit pricey for something that looks so simple, but it sounds like it has a nice feel to it. more like a marker than a pen and soft as to be more appropriate for using to write on expensive glass.
BEST PAINT BRUSH: The Sensu Brush: is the ultimate 2-in-one tool for digital artists. It delivers an authentic painting experience on your tablet or smartphone. The Sensu portable artist brush & stylus works great for capacitive touchscreens like iPad, iPhone, Kindle Fire, Google Nexus S, and other devices.$39.99