Google finally added full support for MMS into Google Voice which means that if you swap devices often as I do, instead of having to switch SIM cards back and forth, I can simply port my main cell phone number over to Google Voice and then point my number at any device I choose.
I tired this a few years ago but at the time, you could not send or receive text messages that included photos or videos. About a month ago, they added MMS support but images came through as a link that had to be clicked. That seemed spammy to me.
I think its time I give it another try. That means that I will transfer my cell phone number to Google Voice and have a random number assigned to my phone. Then if I want to switch between phones, I just log into Google Voice and point my number at another phone. Google Voice makes it easy to point your number at any phone. With Google Hangouts integration, I can get calls anywhere, even on a tablet or my laptop. This has been possible for a while now, I have just held off because I would not have been able to receive picture text messages.