Note: This blog post was originally written to be posted on the Google Wave blog, but did not make it out before the cancellation of Wave. I am posting it here in case it is useful to Wave open-source developers in the future.
When I first discovered Google Wave and started working on its APIs, I realized that Wave had the potential to be a universal inbox one day, using the robots API to collect notifications from all the different inboxes and services that I use. I've since realized that many legacy services don't provide notification APIs but many of them do provide a common integration point - email - letting you specify an email address, and then sending new information to that address. Well, as it turns out, it's very easy to create an app in App Engine that can receive email at particular addresses, and then process that email. Using this technique, I can realize my dream of a universal inbox, by simply forwarding all my services to an AppEngine-powered email address, and appending the email content to a wave in my account.
So, I created the Mail Digester bot to do just that, and open-sourced the code for all of you to base your own mail-receiving robots on. The app starts with a handler for all inbound emails, so it receives emails sent to any [address]@maildigester-bot.appspot.com. It then creates or finds the digest wave for the particular address, and appends a blip with the content of the email, converting any HTML emails to text. For example, if I send an email to "email@example.com", and the app can't find any digest associated with "myemailupdates", it will create a new digest wave and add my wave address. The next time that I send an email to that address, it will find the wave in the datastore, and append a blip to it with the converted email. I wrote it this way so that I could easily create different addresses for different purposes and subscribe to a few different waves.
Once I created the robot, I set to work seeing how many services I could bring into Wave via email notifications. First, I set an address as the issue notification email for the google-wave-resources Google code project, so I could have a digest wave for all the issue updates. Next, I added another address as a member of the Google-Wave-API google group, so I could have another digest wave for new group messages. Finally, I set another address as a Gmail forwarding address, piping all my inboxed emails into a third digest wave. I still need to pop out to Gmail or other services when I need to reply, but in fact, now that I do all my team and community collaboration inside Wave, I find I only need to respond once a day or so.
Using the same principle of using a robot to respond to emails, several of my colleagues have built robots to respond to specific types of notifications. For example, one Wave engineer wrote an on-call robot that parses incoming pages from email and appends them to our weekly on-call wave, so that it's easy for us to discuss the contents of the page. Another food-loving colleague wrote a bot that turns the daily menus into waves, adding images of the food and rating widgets.
Though it at first feels odd to be using email as an integral part of a wave robot, responding to email is actually a great way to integrate Wave with existing services in your organization and even add a collaboration layer on top of them.