The upcoming Leitner-Wise e-Sights are a product that has been missing from the market for a long time now. The e-Sights are basically a minimalist set of back up iron sights that weigh very little and take up minimal space on the rail. Their clever design allows them to fold onto themselves which, when coupled with their already compact dimensions, makes them very unobtrusive.
The reliability of modern optics, especially Aimpoints, is no longer in question. In my personal experiences, I have seen more iron sights break than I have seen Aimpoints go down. In spite of that, all of my carbines have back up iron sights because, while I trust Aimpoint implicitly, I am less sure of the batteries that power them. I change my batteries regularly and have never had one die at an inopportune time but I recognize the possibility that it could happen. That is exactly why it boggles my mind that something like the e-Sights haven’t existed until now (they will be available very soon).
As optics advance, it becomes increasingly less likely that they will fail but Murphy still dictates that it is prudent to have iron sights. Given that the iron sights are a back up sighting system and the likelihood of their use is ever decreasing, it makes sense that they should be as unobtrusive as possible.