One of the beauties of choosing the sun as a source for water heat is that the pool heating accessories solar needs are few if any.
Solar pool heating is one of the best improvement you can make to your pool system precisely because you need to buy very few accessories.
If you use solar heating panels for your inside hot water needs you often need to consider how to get the water moving up to the panel. Of course all pools have a pump already installed for chemical mixing and water cleaning, so oftentimes this just needs to be rigged to the solar paneling.
Sometimes the pump will need to be upgraded, or a small secondary pump can be accessorized that will do the job. For those who really want to go the whole hog, an upgrade that may be worth investigating are solar assisted heat pumps.
Sometimes the solar panels themselves should be thought of as accessories since not everyone wants to place all the solar paneling needed to ensure complete pool heating from the sun. In this case you will continue using a traditional pool heater as well - the solar loop will help keep the bills down. This can also be a worthwhile investment.