Alco Calcium batteries can be a good choice for cars which may be left to stand for long periods (e.g. at airports, or which are only occasionally used). They will never need "topping up" at services - i.e. you can't get to the cells to top them up - they have a chemical added which is designed to scavenge the moisture created by charging and re-cycle it back into the cell.
Our Maintenance Free Range are made in South-Korea by Alco. If you want a calcium Maintenance Free imported battery then we reckon Alco are as good as you'll get in the Australian market.
(Lots of other brands are available, many of which have had quality problems from time to time. Many tend to marketed on very high "Cold Cranking Amps" (CCA) ratings - on the battery label at least. This seems to be achieved by cramming in lots of (thin) plates to bump up the plate surface area, often at the expense of reliability. They generally don't test up at their CCA ratings in reality - even when new).
The downside to Calcium MF batteries tends to be that they are very hard to recover if they ever do go flat (e.g. lights left on in the car). You need a good battery charger with a Calcium (High Voltage) stage to properly charge them - something many battery chargers don't have.