It should work in nearly all countries -- anywhere that Twilio can send SMS messages. The app's number is based in North America so there might be international texting charges depending on your provider, but I'm planning to set up more numbers based in different regions.
Trying it from the Czech Republic (+420). I got the welcome message withing few seconds and replied, but the server probably never got my reply ("Looks like you were sent a welcome text but didn't finish setting up your account")
I think this may be due to a limitation of Twilio's toll-free US/Canada numbers -- looks like they sometimes have issues with global SMS. It should work if I set up a standard local US number and use that for international users. Thanks for spotting that bug!
