Heybuddy

It's not yet there where Gravity for Symbian is but still outruns Mauku by far. It has Tabs for mentions and can follow conversations (contexts). It also features sort of filters for groups and users but either it is not yet fully implemented or I just did use it wrong.

What still is missing is the possibility of alerting for specific events like e.g. a mention (@-reply) or that you can subscribe/unsubscribe to users and groups. Also, it only works with identi.ca but not with other sites that run status.net.

Still, if you own a Maemo device and are on identi.ca, give Heybuddy a try!