This Multi-Touch Vista project on codeplex provides a Windows service which emulates a touch screen, with multiple touch points. You can use this service to test multi-touch apps even if you don't have a device.
To install this service, follow the steps from the download page.
Alternatively you can watch this quick video tutorial:
Tip: The driver worked for me correctly on Windows 8 only when I installed it as a Windows service. Make sure to block the native Windows mouse input in the configuration utility (Multitouch.Configuration.WPF.exe) after having the service running.
After installation, services.msc should report the Multitouch driver under services:
The multi touch service installed as Windows service.
Start the service and set the configuration.
The configuration tool with the blocking native mouse option. The red dots represent my two usb mice connected to the computer.
Note that it can take some time to get used to get used to the multi-touch emulation.