Identity cards for foreign nationals (Accra)

Yesterday I saw an advert in the Ghanaian times about foreign nationals needing an identity card. Today I went to the CAL bank at Ridge and went through the process. It cost US$120 or cedi equivalent and was issued there and then.
There doesn't seem to be any real purpose in having one although it does help with bureaucratic things like getting a driving licence or bank account and dealing with some gov dep.
However there is a penalty for being in Ghana for longer than 90 days without one