Just a rehash of Maxroam. Their sites are identical. Have a look at:
SeaRoam - Frequently Asked Questions
MAXroam - Frequently Asked Questions
Without sounding too negative... as it is a rebrand of Maxroam, I suspect the price calculator may well have to be taken with a pinch of salt! Also, not sure if the claim that you can forward your Belgian number free of charge to 50 destinations worldwide is completely accurate either!