Daisy-chain to me means it would be a "parallel setup". In this regard, it would act on the whole as if it were one unit. While, that appears to seem OK, you may experience some difficulty as the electronics of a UPS while simple or any s/w based one would act sluggish, IMO. Also, I would think the 1st UPS of that chain would get the most punishment and not necessary show as the remaining UPSs, allow it to be so. In the long run, you're defeating the purpose of the UPS. Use the UPS as it was intended for certain devices and allow it to act accordingly. Actually, if you have real bad power issue on a constant basis, get the largest UPS you can afford and plug the same devices you would have on a smaller rated UPS. YPS are intended for a controlled shutdown usually PCs. Any other electronic device maybe better served by a surge protector of a higher rating than simple protectors as they really don't need UPS, though they can be plugged on. Understand, most simple UPS setups are in fact simple surge protector too, many aren't that high rated. Of course, it wouldn't hurt to have direct plug-in surge protector on an AC cord that yet plugs in to a UPS. remember, surge protector do fail if "used", the MOV component breaks down and its done, has to be replaced. A simple surge protector or a cord type can be tossed saving the UPS surge protector circuit if not done in. Check the websites of APC and Tripplite to better understand UPS operation.
I am a UPS fanatic. Living in Florida, I think we have the "dirtiest" electricity as far as brownouts and other surge problems go. I know surge protectors only filter out the spikes and it requires a UPS to "add" the necessary electricity during a brownout which we get all the time. So I have them on everything including the garage door.
Some years ago, when Circuit City was going out of business, I was able to buy a bunch of 1000VAC UPSs for cheap. They supply about 600 to 650 watts of power for anywhere from fifteen minutes to an hour depending on just how much you are drawing from them.
I actually have a couple more than I really need right now so I was wondering, what would happen if I "daisy-chained" a couple of them? If we had a power outage that lasted a couple hours, which is not all that unusual here, would not the second UPS in line think all was fine while the first one was running down and then the second one would take over and start its cycle of running down? Could you prolong electrical supply for an indefinite period if you daisy-chained an indefinite number of UPSs?