I want to be able to have a second phone number that I can use from my iPhone that supports calls as well as inbound and outbound SMS.

I've been using Voip.ms + Bria for a long time, and while the calling portion works fine, SMS support is limited... Bria supports SMS over SIP, but Voip.ms doesn't... Voip.ms lets me forward inbound SMS messages to my cell phone number, but then to respond, I have to log in to Voip.ms's website. So it sort of works, but it's clunky.

Are there any providers that do support SMS over SIP/IAX2, so an app like Bria can be used for both calls and messaging? Ideally one with a similar feature set to Voip.ms as far as call handling rules. And I know no one really comes close to Voip.ms's $0.85/month rate for pay-as-you-go DIDs, but this is for sporadic use and not something I'm looking to pay double digit monthly rates for.

Any thoughts?