I live in an area of frequent power cuts and interruptions. When the lights go out, I need internet access to check on the fault and timescale for a resolution. This is impossible if the homehub has no power. I don’t want the cost or capacity of an uninterruptible power supply and since the hub only requires DC power, a battery backup (as per my laptop and phone) is all that is required. I imagine that for about £20 BT could supply a pack which fits behind/under the hub with a 6000 – 8000 mAH lithium battery and would keep the hub operational for 4+ hours. It could even use the plug in power supply from the hub, thus saving the cost of a new one. An LED indicator to show if it is charging/discharging and something to show remaining battery life would be useful.
I've seen a plug-in one on the internet, but not a DC in - DC out version.
Just an idea, but I bet it would be very popular.