Tell me more...
Not much to tell.
fi.google.com is the website.
You sign up for a SIM a couple of weeks before your trip (if you don't have one already).
Download the app to your phone, and insert the SIM on the way to the airport (though I believe with iOS you might need a WiFi connection so you might have to do it at home). Select your plan, and after an hour or so it is provisioned and you can use it almost anywhere for the same rate as the US. International calls are an additional fee, but fairly cheap.
They have two plans one has a base fee ($20 for a single line) and $10/gb used up to a max (6 GB max on a single line), or if you know you are going to use more than the max, you can sign up for an unlimited plan ($70 for a single line). It seems expensive, but unless you don't use much data it is pretty price competitive for SIM travel plans. I know on one trip I spent $80 on Vodafone top offs because hotel WiFi was $10 a day. In Japan I used 15GB of data on my 3 week trip (again because many hotels had pay of WiFi or it was so slow it was unusable).
You can also loan the SIM to others. My mom used my SIM on her trip to Europe last year.