The part about tying in all your SIM cards when travelling is interesting to me. I'm constantly across borders and I don't yet have a cost-effective solution to getting SMSs on all numbers (Skype works fine for call-forwarding).
That I could forward my numbers locally to a number I choose. Say my U.S. cell, Australian, UK and Spanish cell phones: I just buy a new SIM when I'm back somewhere longer than a few days, but that's getting ridiculous (though it's cheaper than roaming). If I'm away for a while it expires, so I get yet another number. I could email everyone or call them but they have an old number for me and it's a hassle for my friends, less me as my Android phone is great at keeping me up-to-date.. so maybe it's something as simple as an iPhone/Android app that pushes cellnumber changes to your friends? I'd pay for that. I can't imagine the telcos letting go the noose on their number forwarding..
I understand what you are looking for, and I think it could be achieved as a tier 2 telco... in the meantime, here's something that might be better than your current solution (no affiliation): http://www.worldsim.com/featuresMulti.aspx
Yes, if additional numbers were actually priced well. Skype for example, you're paying 20-50cents a minute for forwarding to non-U.S. cellphones so that's worse than roaming in some cases. It's a telco issue basically: cell phone calls are ridiculously priced outside of the U.S. and Canada.
While I'm not sure I would use this as "more personal, more emotional" texting - I'd still just call - I see the value for lessening misunderstanding. Texting is pretty low bandwidth, by comparison.
