Tell people to set up a Kaywa ID* in advance either by going to http://id.kaywa.com or by sending an SMS to 202 with NEWID username (Swisscom and Sunrise, CHF 0.20).
Advantage: With SMS you can also set it up right at the place.
Now people can simply check in. We can provide:
- Sticker where people have to click a link to check in (default)
- Sticker code which is the checkin
After the meeting or conference we can provide the list of people who have checked in.
At the same time, people have also get a direct communication channel and people from the outside can tune in.
* Kaywa ID is Open-ID enabled by the way