Mono is a greate solution for anyone looking to do some cross platform development. Most of the .Net API has been implemented and functions the same as Microsoft’s version. Although, one thing that does not work under OS X is the serial port.
This seems to be a known issue with the Mono devel team, however, at work we rely heavily on communication over the serial port and needed a solution fast. Therefore, I reimplement the serial driver for OS X. The new version does not rely on the libmonoposixhelper but rather creates a wrapper for the standard libc functions. Most of the API is the same as .Net/Mono and therefore should be easily interchangable.
The OS X serial port is available on the downloads page.