Use an intercom system or baby monitor to alert others that there is an emergency.
Use bells or buzzers if you are not able to speak. Use "codes" that signify urgency. For example, a tinkling bell may mean, "I'd like company" while an air-horn means there's an emergency.
Carry a portable phone that is equipped with pre-programmed numbers.
Pre-program all of your telephones so they can automatically dial the necessary emergency number(s).
Consider a "life call" button if you spend time alone.