TouchDown does not sync with other apps.
TouchDown was designed to be secure, and since we cannot attest to the security of the native applications (phone book, calendar, etc.), TouchDown will not synchronize with any other application. The native apps are not able to load information from TouchDown, except for a one-way "copy to phone" function in which you can copy your TouchDown contacts to the device. However, you cannot copy phone contacts to TouchDown or synchronize any other calendars with TouchDown's calendar. This ensures that none of your private data will ever be sent to or stored on any other server other than your Exchange server.