Thanks in no small part to T-Mobile's free global data initiative, US carriers have begun to lighten the fee load when it comes time to roam. But you'll still pay an arm and a leg in many countries, and discounted plans from AT&T and Verizon, while more reasonable than they once were, require a monthly subscription that can be a hassle to add and remove. If you're expecting to use gobs of data abroad, KeepGo's disposable-SIM program is probably your best bet, but an intriguing alternative from KnowRoaming will keep leisure travelers and other casual users connected in 220 countries without the need to worry about coming home to an enormous bill. That solution, an incredibly thin card with passthrough leads and an adhesive back, simply sits atop your existing SIM, springing into action whenever you arrive in a foreign country. Join me as I travel to Europe and beyond to see how well this sticker works.