Is there any tool to check in attendees on event's day?

Yes. You can find our checkin app under:

https://access.stagehq.com/acc/YOUR_SUBDOMAIN

That is, if your subdomain is 'linkingpaths' (for http://linkingpaths.stagehq.com), you can access the checkin app under:

https://access.stagehq.com/acc/linkingpaths