Short answer:
For home use - no. Price is to high, subscription fee is show stopper for me.
Long answer:
Home use
Why will be home owner or tenant bothered by power use?
First group - people bothered by energy cost. The calculation is simple: the cost of hardware and accumulated subscription fees has to be recouped by energy cost savings in one year.
Yearly subscriptions fee $120, hardware cost, say, $200 gives $320 cost of the first year use of the service.
Energy cost $0.1 per kWh so we have to save at 3200 kWh per year to break out our investment.
3200 kWh per year means, if power consumption is constant, reducing energy draw by about 0.37 kW.
Doable, but is it easy?
Replace incandescent light bulbs by more energy efficient compact fluorescent light bulbs or led light bulbs. Done.
Is cost sensitive home owner the target group? He can be if the price is right. Read - low enough. So - mass production, lower cost per hardware unit, lot of subscriptions sold on ongoing basis. Well, there is one problem. Up front spend on hardware batch. And second one. How to reach these cost sensitive home owners? Marketing. Which means more money up front. Which means more risk. By the way, that means competing on price what is not the best idea for someone starting with limited funds.
Second group - people bothered by Earth future, global warming.
Each saved kilowatt hour means less about 2.3 lb (1 kg) of CO2 emitted to atmosphere. Saving 3 kWh daily during a year means about 1000 kg less CO2 emitted to atmosphere.
How reach people bothered by Earth future? It looks little bit easier. Is it easy enough?
Third group - early adopters, geeks looking for new gadget.
The new cool gadget has a little drawback. It is clipped on the electrical wires, presumably in the hidden electrical box. How to show it to other geeks? There is website with fancy graphs, twitter integration, facebook integration and, of course, iPhone application. And some game mechanics, a little competition: who has smaller energy consumption, who is greener so can be awarded by, say, more images of green leaves. Or bigger tree image. Or blue ribbon. Or ...
This group looks easier to target. It has another nice feature. Virtually all of them can be called linkerati, which leads to some nice side effects. Links, SEO, boost in visibility.
Industrial and commercial use
One 10 kW motor working all year long uses 86400 kWh. Let's assume energy costs $0.05 per kWh. Yearly cost: $4320.
Completely different game.
Industrial environment is harsh. Electromagnetic noise level is really high despite all countermeasures. Current in wires is hardly sinusoidal because of all theses nonlinear power receivers (eg. frequency converters).
What savings are possible in industrial environment?
Use less energy. Use GridSpy for ad hoc power monitoring during machine tunning. Possible for air conditioning, refrigeration, making compressed air, pumping.
Use cheaper energy - prices vary during the day and week. Locating low hanging fruit.
Do not pay for use more power than contracted. Add an ability to alarm someone if there is to much power drawn, allow to change the formula for power calculation. Example: power calculated as 15 minutes average or an 1 hour average.
Do not pay for too low power factor. Power factor monitoring and alarm someone.
Another beast is data reflecting production put on the internet. I know, passwords, vendor commitment to security etc. but ... Btw. this concern exists for home use too.
Despite that all energy conservation is an interesting field.