It doesn’t look like Lifesum has an IFTTT or Zapier integration. Does it send confirmation emails or summary of your day’s activities? It might be possible to hack up a kind of unofficial integration, using IFTTT or Zapier, using something similar to what I described here:
It might not be exactly what you want (which may indeed require an official integration or a programming skills to get a script running somewhere) but you might be able to come up with something helpful. For example, if Lifesum sends you a daily email with a slightly different subject when you’re sticking with your plan vs. not sticking with your plan, you might be able to map those to a binary 0/1 Beeminder goal.
Anyway, thanks for sharing the tool.