Raffi Krikorian of Synthesis Studios wrote to inform me that they've reverse-engineered how the Starbucks button works. Most of the Starbucks shops out there aren't going to get the hookup with wi-fi for about a year. I asked them about it, and they'll be disclosing the process soon.

"we managed to figure out how to get the starbucks button to show up on our iphones -- [if you happen to be in] Boston, MA -- then you can pop by our offices to check it out. we were too impatient to wait for the starbucks in boston to get the starbucks button our iphones, so we took matters into our own hands :P
It's always nice to see folks making their own fun. This fun was apparently done with a laptop, an iPhone, and a train ticket to NY, as you can see here. Thanks to Raffi for the tip!