You’ll be getting a lot of “can it work with…” or “can it…”
What I would keep in mind is to early on develop around integration/exposure to a service like IFTTT and/or Zapier.
This way you can expose actions and triggers and users themselves can setup “recipes” (IFTTT) or “zaps” (Zapier).
Examples:
- If new Evernote note in XYZ THEN create new Everdo inbox item
- If new Everdo Due Date THEN add to Google Calendar
- If Everdo item completed THEN add to Google Sheets
- If Everdo item due THEN switch on my Philips lightbulb
etc.