I'm not sure what the point of this would be. In the United States, the accountability that is important during elections has very little relation to the result

I'm not sure what the point of this would be. In the United States, the accountability that is important during elections has very little relation to the results of the legislation that a congressmen voted on. In other countries, like the UK for example, the only accountability that most MPs need is that they voted consistently with the party line. It's sort of a flaw in democracy that voters will be fully informed about their elected leaders and within one election cycle will be able to judge how effective a leader or congressman turned out to be. An always on-the-record congressman wouldn't make any of that better.