Had an interesting call earlier with LogicaCMG, a company with a long heritage in SMS and MMS, and which has a fairly messaging-centric view of the world when talking about IP and IMS. Aside from its current pitch around converging different messaging types onto one platform, another topic which cropped up was a new standard agreed by 3GPP a week or so ago.
Called TS 24.341 this is basically an agreed standard for supporting receipt & transmission of SMS over an IP network - eg from a dual-mode phone connected in WiFi mode.
Now, being 3GPP, the whole thing is clearly very IMS-centric, involving the usual registration of a device with an alphabet soup of HSS and CSCFs. I haven't had a chance to wade through the whole thing, but it certainly looks like it's been designed with some specific problems in mind. What's not immediately obvious to me is whether the same approach (or a similar one) will work outside of IMS, so that (for example) a VoIP provider or an enterprise with an IP-PBX could also deploy an IP-SM Gateway.
As I mentioned a month ago, the whole VoIP+SMS issue is a critical one now, especially for the new breed of mobile VoIP providers. I hope they can use some aspects of the new standard to solve one of their more intractable problems - and I encourage both infrastructure suppliers like LogicaCMG and their handset SMS-client software counterparts to consider both operator- and non-operator use cases for SMS-over-IP in their product development roadmaps.