With the online Will, how do you know when I've died?

Our service is called an "online Will writing service" but there is nothing "online" about your final Will. You are simply going online to create your Will.
You step through our service to prepare your Will. But once you have answered all of the questions, you download and print your final document. This final document must then be signed in the presence of two witnesses who cannot be beneficiaries in the Will (they do not have to be of any social standing or legal professionals, just two adults who will not gain anything from the contents of the Will).
The law only accepts a Will that is written on a piece of paper and signed in ink in the presence of two witnesses, who also sign the document. The online version of the document is there for your convenience only. It allows you to quickly and easily make updates whenever your circumstances change. But anytime you update your Will using the online service, you must print a new version of the document, which again, must be signed and witnessed.
Once you have your printed Will, we are not involved in the process at all. Within the Will you name your "Executor". This is the person who has responsibility to carry out the instructions in the Will. After you have passed away, your Executor presents the Will to the probate courts where it is accepted as your Will and the Executor is given a "Grant of Administration". This document allows them to gather up your assets from the bank and other financial institutions.
You should choose an Executor who will know that you have died. It is also important that your Executor knows where the Will is, and that they have access to it at the appropriate time. Some people just give the document to their Executor in a sealed envelope for safe keeping.