Getting accurate watch counts from eBay is problematic. There are two different calls to get listing info at eBay. One returns smaller amounts of data on all listings that have had selling or bidding activity, and another returns much more data, but only on one listing at a time. The second call is the only call that returns the watch count.
We make the broader call every 15 minutes to find out what has changed and then make the more detailed call on just those listings. This is necessary to make sure the refresh process is as fast as possible.
The only way to ensure timely up to date watch counts would be to make the detailed call on all listings every X minutes which, depending upon the number of listings you have, make SixBit simply churn with continuous update calls.
Without up to date watch counts on all listings, it would be hard to implement something like this.