The Solar Arc is a bit of a gimmick, it probably does warm the water some, just remember heating a pool is not about adding a little bit of very warm water it is about maximum thermal transfer which usually means adding a whole lot of only very slightly warmed water. As Jason says solar pool heaters are all about surface area, there are only so many watts of heat per square foot of sunlight, and under typical swimming weather conditions those big black plastic panels are surprisingly efficient at sucking it up, there just is not that much room left for magic small panels to do anything extra except give the impression of heating by supplying a small amount of very warm water.
Ike