This week's talk of the planned Facebook initial public offering got me thinking about a story from late last year: Which mobile health company is likely to IPO first? Some investors have already placed their bets.

At the end of November last year, investment bank and securities firm Goldman Sachs held a quiet, stealthy event that included presentations from about two dozen startups that the financial firm reportedly believes are likely IPO candidates in the future. The event is intended to help Goldman cozy up with these promising startups early on.

According to the list pieced together by TechCrunch, among those early-stage companies that received an invitation to the event there was only one health-focused company: ZocDoc, a physician and dentist appointment scheduling site and app.

Jawbone, which offered up the Jawbone UP fitness device last year (and promptly offered full refunds to early buyers because of bugs), also presented at the conference, but its core business is Bluetooth earpieces and speakers -- not health devices.

ZocDoc allows patients to find nearby doctors who accept their insurance, then book appointments, via Android and iOS apps, as well as a web-based interface. The service is free for patients, while doctors pay a $250 monthly fee to fill open appointments.

Last year ZocDoc pulled in about $75 million from investors. In August DST Global injected $50 million into the company. A short month later Goldman Sachs itself made a $25 million strategic investment in ZocDoc, which boosted the company's overall investment total to close to $100 million.

Given its $25 million investment, it's no surprise Goldman picked ZocDoc to present in November.

For more on the Goldman Sachs event, read this TechCrunch post.