Research firm Technology Appraisals has published a report, Low Cost & Mobile VoIP: Mobile Communications, which looks at the low-cost and free international mobile calling sector. The report notes that companies such as mig33, Truphone, EQO, fring, MOBIVOX, iSkoot, cellity, JAJAH, Vyke, and Rebtel have  attracted VC funding and hit the headlines by offering low cost and even free international mobile calling, often combined with new mobile applications including IM (Instant Messnger) chat, buddy lists, and social networking.
Despite the progress, it is a very confusing area, says Tim Riley, Co-author of the report. Once you get beyond the headline benefits claimed for users, and the inevitable marketing hype, you realise there are important issues that dont come out unless you take the time to dig deep, such as ease of use, roaming capabilities, what handsets does it work on, availability of wi-fi, and what is really free.
The report notes that the new services also use a range of fundamentally different technical solutions, including wi-fi, 3G data, call-back, call-through, local numbers, mobile web, and SIM cards, implemented in different ways, and each with its own distinct advantages and disadvantages. The report concludes that its difficult for consumers to find out what is really on offer, what it can really deliver, and to make comparisons.
The report costs 375 (plus VAT for UK organisations) for a 1-5 user electronic copy. Theres more information on the report here.