CALIcamper,
That unit does look interesting but researching it I found this comment:
It should be noted that this and most other similar devices available today work only on the 2G network, which is systematically being phased out by most carriers by end of 2016. The H2O card mentioned works on the AT&T network. If, like me, AT&T has already phased out 2G coverage in your area, T-Mobile may be an option. If so, look for PTel prepaid sim card, which works on T-Mobile network. Make sure you check 2G coverage in your area before buying, or you will likely be unhappy with the results.
Can anybody shed more light on this?