If you do a search you'll see this has been an issue/request with the Ally for its entire lifespan. Even though there are numerous apps out there that are able to play with the LED and do it successfully on other phone models, the Ally just doesn't cooperate. You can try some of the full-featured LED apps, and at most you'll be able to get the color to change and make the LED "remind" you at a set interval, but as far as modifying the actual rate and pattern of the flashing, I have yet to see anything that can do that.