You can use the version that is in the plugins database with 2.1:
It won't be updated any further, as that will be done in the 2.2+ version, but it should work decently.
Thank you for your input!
I get the following notification:
"Plugin "theme_mymobile" (2011101801) could not be installed. It requires a newer version of Moodle (currently you are using 2011070100.02, you need 2011070101)."
So It requires release 2011070101...
you need to select the version that is compatible with 2.1:
Ok. Thank you Daniel.