Many people forget that before the advent of femtocells, a similar technology - picocells - has been around since 2001 or earlier. Picos have more capacity, but are considerably more expensive than femtos, and have required more expensive controllers and specialised installation procedures.
While many picos have been deployed by mobile operators for cheap "fill-in" coverage, or used in niche locations like oil rigs, ships or small islands, a more interesting business model was "Low Power GSM", pioneered in the UK with the auction of the 1800MHz DECT guard band four years ago. This enabled multiple new operators to bid for low-cost licences for indoor wireless services, using a thin sliver of unused 2G spectrum - especially enabling low-cost or free indoor private cellular.
I wrote about this here and closely watched the evolution of service launches, although uptake out to be comparatively slow. Cable & Wireless launched a corporate service for clients including Tesco, and Teleware has had some success with its Private Mobile Network. Two years ago, the market status was still limited.
One of the big problems has been for the new "indoor" operators to gain some sort of MVNO or roaming deal with the incumbent "outdoor" service providers, so they can provide a universal mobile coverage service. Perhaps unsurprisingly, the traditional "macro" operators have been unwilling to assist their new indoor-only cut-price competitors.
But something more interesting is occuring in the Netherlands. I wrote about 4 months ago that LPGSM was being enabled on a licence-exempt basis. And one of the companies that is now exploiting it has solved the indoor/outdoor conundrum, as it is *already* an MVNE, operating on Vodafone's Dutch network. Teleena announced its converged service yesterday.
Now obviously this is just GSM - so perhaps not much use for today's 3G smartphone-toting executive who finds that data services are sent over EDGE when in the office. Nevertheless, I'm considerably more positive about this type of approach than enterprise femtocells, which I continue to believe are unlikely to make traction for many years.