another interesting company in this space is FlexiroamX, they have a super flat sim that sticks on top of your existing sim. It lets you soft-switch the SIM using a "SIM Application" (like mentioned elsewhere in the thread) - appears as if it unplugs and replugs to the phone.

See picture of the process here: https://twitter.com/lathiat/status/758979125751054336

Works fantastically and gives me $30/GB data in pretty much any country at often 4G speeds - with a 12 month expiry on the data (does cost $20 a year or something for 'membership' but still, usually costs far more than that for a sim starter pack in every different separate country you go to). Good for frequent travellers!

Obligatory please use my referral link if you signup :-) Bonus 100MB for both me and you. http://www.flexiroamx.com/referYXBBCJ / Code YXBBCJ

Super interesting. So the overlay tricks the phone into thinking there's 2 SIMs in the phone?

It's more like a "proxy" for your SIM card where it can act as its own SIM, or as a passthrough, depending on software settings.

>$30/GB

Some European operators still have cheaper roaming data plans

As an example, I pay £20/month for 30GB, that can be used anywhere in the EU, USA, Canada, Australia (and a few other countries).

If it's "Feel at home" from Three, you can use it only for short trips and tethering is forbidden.

Sure, they do remote provisioning, but it's not eSIM in that there is still a sim card! I assume they use some special USSD codes to switch to their provisioning carrier and use a normal network connection to do that.

In the case of a true eSIM, there is no sim card at all, it's stored on the device it's self with a lower level bootstraping profile (i.e. not an alternative pre-programmed carrier)