>You can set up a side channel between your own devices to sync that history.
Then
1. Some device would need to be logged in and online (not always true)
2. You'd need a way to authenticate the new device, which means not only do you need the other device on, but you need it close when first setting it up, and you'd need to manually transfer keys or something of similar bandwidth
3.Either all history would need to transfer, which is a bandwidth hog if history is large (although if device is close then you could transfer over Wifi direct or bluetooth or something), or that other device would need to kept online whenever I want to query history (currently, Google serves this function)
4. If you lose a device, there's no recovery (this is probably the main reason Google won't do it.)
If you really want it, there are apps that do E2E and support Google Talk. See https://chatsecure.org/
Then
1. Some device would need to be logged in and online (not always true)
2. You'd need a way to authenticate the new device, which means not only do you need the other device on, but you need it close when first setting it up, and you'd need to manually transfer keys or something of similar bandwidth
3.Either all history would need to transfer, which is a bandwidth hog if history is large (although if device is close then you could transfer over Wifi direct or bluetooth or something), or that other device would need to kept online whenever I want to query history (currently, Google serves this function)
4. If you lose a device, there's no recovery (this is probably the main reason Google won't do it.)
If you really want it, there are apps that do E2E and support Google Talk. See https://chatsecure.org/