7 Wh/m^2, if we consider a typical medium-sized residential apartment with floor and walls (and possibly ceiling ), then perhaps it could store around 2 kWh totally (at least, that's the order of magnitude we're talking about). That's possibly a bit more than a typical Li-Ion battery on an electric bike, but not very much more. Well, difficult to say without knowing the energy density per volume (Wh/m^3). Perhaps it's needed to stack several layers of such batteries to make a solid outer wall or a solid horizontal floor/ceiling-layer, then maybe the number may be multiplied with two, three or four.
I think one good use case would be to build a residential apartment building, cover it with solar panels, put a windmill on the roof and have sufficient storage capacity in the building to at least get through a typical*) dark night with no wind. Unfortunately, those batteries does not seem to have sufficient capacity for that, so to get through the night one would probably end up installing Li-Ion batteries in the basement - then it would probably be easier and cheaper to install some few more batteries in the basement instead of providing walls and ceilings with power distribution infrastructure (one could possibly also stack more cement batteries together - but there are limits to that, one probably wouldn't want to have several meters with cement between each floor in the building, or have outer walls that are several meters thick).
For other purposes (i.e. powering LED-lights on a bridge throughout the night, sensors to check the integrity of said bridge, etc) it may possibly be great.
Costs are of course another question - if the extra price for building concrete blocks with built-in battery functionality as compared to ordinary concrete blocks is too high as compared to Li-Ion batteries, then it's not profitable. Actually, for changes to happen (on a bigger scale), the cost of "cement batteries" actually needs to be far less than Li-Ion batteries - we're talking about a conservative well-established industry, doing changes involves taking risks, and it's needed with good incentives for that to happen.
*) I've grown up with two months of constant daylight in the summer time and two months with no sun in the winter time, so that's what an "atypical" night and day may look like