bp_last_activity( int $user_id )

function bp_last_activity( $user_id = 0 ) {

	/**
	 * Filters the 'active [x days ago]' string for a user.
	 *
	 * @since BuddyPress 1.0.0
	 *
	 * @param string $value Formatted 'active [x days ago]' string.
	 */
	echo apply_filters( 'bp_last_activity', bp_get_last_activity( $user_id ) );
}