The Walmart where I regularly shop switched to digital shelf tags a while ago.
There really is no practical opportunity to personalize pricing using these. Suppose Walmart were tracking a customer through the store and figured out that the customer met some demographic that would pay more. If it updated the shelf tag as that customer walked by, no other customer would see that price (as it would revert immediately after the targeted customer left the area). Furthermore, the record of that higher price would have to persist all the way through staffed registers and self-checkouts. If the customer returned to pick up a second jar of the item, and this time there was another cheap customer also in the area, would the system raise the price on the shelf tag again? If not, would it figure out that the first jar was $10 and the second jar was $8? What if the customer put the first jar back on the shelf and then picked it up again immediately -- would they then pay $8 or $10 at checkout?
Frequent price changes are simply not practical in general during operating hours. At least in my state, the rule is that the price you pay must be the price on the shelf (although I think the retailer is free to charge a lower price at the register), so changes would have to take into account the lag between a customer picking up the item and going through checkout. They could probably post a prominent sign saying, "Shelf tag prices are good for a maximum of two hours." Then, for price increases, they could update the tags and wait two hours before updating the POS system. For price decreases, they could lower the price in the POS system and update the shelf tags two hours later.
Since the digital shelf tags were rolled out at my Walmart, I have a subjective feeling that the prices do change more frequently, but I lack objective data on this. I have no problem with this.
One cool feature of the shelf tags at my Walmart is that, with the app, you can look up a product and the tag will, on request, flash a blue LED so you can find its shelf location quickly. Of course, this being Walmart, there's a pretty good chance that the item is out of stock or that the item in that location isn't the item that's supposed to be there!