According to the manual (the radio has not been delivered yet) you can add streams through their web site.
From the manual:
If you want to listen to a station or podcast that is not in the Reciva stations list, and you know the streaming url for the station, then you can add it to your own personal list of stations. This is entirely personal to you.
On the Grace website, please log in and then click on ‘Manage My Stuff’, and then click on ‘My Streams’ or ‘My Podcasts’.
From this section of the website you are able to search for your personal audio content provided you know the streaming url. As with My Stations you can organize your list into folders and keep personal notes about the content.
Next time you use your radio, under the My Stuff icon you will find My streams. Selecting My Streams will show the stations you placed in My Streams, and similarly selecting My Podcasts will give you your podcasts.
The user manual can be found on this page: http://www.gracedigitalaudio.com/mondo-p-212.html
It uses more than just free streaming services. It works with the paid version of Pandora and SiriusXM. There may be others but I have not looked into it more than that yet.
Tar, feathers, congress. Some assembly required.