bp_core_record_activity()

function bp_core_record_activity() {

	// Bail if user is not logged in.
	if ( ! is_user_logged_in() ) {
		return false;
	}

	// Get the user ID.
	$user_id = bp_loggedin_user_id();

	// Bail if user is not active.
	if ( bp_is_user_inactive( $user_id ) ) {
		return false;
	}

	// Get the user's last activity.
	$activity = bp_get_user_last_activity( $user_id );

	// Make sure it's numeric.
	if ( ! is_numeric( $activity ) ) {
		$activity = strtotime( $activity );
	}

	// Get current time.
	$current_time = bp_core_current_time( true, 'timestamp' );

	// Use this action to detect the very first activity for a given member.
	if ( empty( $activity ) ) {

		/**
		 * Fires inside the recording of an activity item.
		 *
		 * Use this action to detect the very first activity for a given member.
		 *
		 * @since BuddyPress 1.6.0
		 *
		 * @param int $user_id ID of the user whose activity is recorded.
		 */
		do_action( 'bp_first_activity_for_member', $user_id );
	}

	// If it's been more than 5 minutes, record a newer last-activity time.
	if ( empty( $activity ) || ( $current_time >= strtotime( '+5 minutes', $activity ) ) ) {
		bp_update_user_last_activity( $user_id, date( 'Y-m-d H:i:s', $current_time ) );
	}
}