So I have been working with the Pocket PC Notification Class within the Compact framework 2.0.
It's a great little class and I love the fact you can use it and it will make your application feel a part of the OS...
It's so easy to create a custom bubble too...
Add the Notification control onto your main form
then using this component we can customise it...
The Caption
notification1.Caption = "Bubble Caption";
The body... Now rather than just a plain text body, them guys at MS thought "I know lets make it HTML".... SWEET!
StringBuilder str = new StringBuilder();
str.Append("<html><body bgcolor=\"000000\">");
str.Append("<font color=\"#FF6600\"><b>Notification Bubble</b></font>");
str.Append("<p align=\"right\"><form method=\"GET\" action=notify>");
str.Append("<input type='submit'>");
str.Append("</body></html>");
Now set it...
notification1.Text = str.ToString();
You can change the length of time (in seconds) for the Bubble to say on.
notification1.InitialDuration = 5;
then just make it visable...
notification1.Visible = true;
Now this is where it can get really cool... If you build event handles to it like
notification1.BalloonChanged += new BalloonChangedEventHandler(OnBalloonChanged);
and
notification1.ResponseSubmitted += new ResponseSubmittedEventHandler(OnResponseSubmitted);
You can do thinks like, Dismiss the reminder, but come back to it in 5 mins... Or do something on the screen directly from the buble WHILST it's shown! Now that's cool!!!
My only gripe... No image capabilty... You'd think I'd be able to put an image in there too... O well... Maybe in release 3? 
(EDIT: Due to layout issues)