Segger are offering a free firmware upgrade to be applied to ST Nucleo's on-board ST-Link.
The upgrade promises to turn the on-board ST-Link hardware into something "compatible to J-Link OB".
The one feature which caught my eye is "Virtual COM port (VCOM) support"
There are various restrictions though, for example:
The firmware may only be used for development and/or evaluation purposes. It may not be used for production purposes.
It might be useful to someone who has a development system which supports the Segger J-Link product.
They appear to include instructions on how to restore the origonal ST-Link firmware, which begs a few intriguing questions.