Customer group products only

Is it possible to create products for them only to be seen by a certain customer or customer group?

Well yes but this would require people to be register and to be logged in. I checked the shop and I say no extension that performed this. Someone would need to assist you in doing this but I can tell you what it would take:
1) Upon product insert/edit you would want to assign a cust_group_id to the product (if any at all). This would be a new field in the product table set up as an int(11).
2) You would need to alter the way products are displayed by running a conditional where first you get all customer_group_id's then you display products tied to those customer_group_id's ELSE display all other products (products not tied to a customer_group_id