Another Alternative, with less features
Ok, Now for all of you who have yet not joined, buddydev Premium, well, you can use an alternative.
Put this code in bp-custom.php and None of the site admin activity ime will be recorded.So if you are a site admin, you will never appear in the Who is Online/ recently active members widget.
12345add_action("plugins_loaded","bpdev_init_sm_mode");function bpdev_init_sm_mode(){if(is_site_admin())remove_action("wp_head","bp_core_record_activity");//id SM is on, remove the record activity hook}