Putting a Power of Attorney into Effect
A durable power of attorney can be drafted so it becomes effective as soon as you sign it. Alternately, you can specify that it will not become effective unless a doctor certifies that you have become incapacitated. This is called a "springing" power of attorney. It lets you keep control of your affairs until you are no longer capable of doing so.
A LegalZoom Durable Power of Attorney includes a "springing" option.