I use the convert functions at coinbase to take advantage of market changes to increase my position amounts.
This weekend I am going to write a php script that tracks the available conversion pairs and makes charts & notifications when a coin you are holding has increased in price and swapping coins may be beneficial.
Example: 5 BCH = 8 ETH. BCH increases by 5%, now 5 BCH = 8.4 ETH. You make the swap and wait. BCH retraces AND/OR ETH increases in price... Maybe now 8.4 ETH = 5.06 BCH.
The end result in the example is an increase of .06 BCH.
Does Coinbase offer an API for the convert functions? Could not find it...