Extending watches with apps is one thing if you're building for a smartphone companion with a traditional, developer-centric app model. It's quite another when it's a GPS watch, and athletes are building their own apps -- yet that's what Suunto has managed with a 2.0 firmware update to its Ambit outdoor watch. The revamp uses a simple web interface to let us build free sports apps based on criteria as simple as distance and speed through to more specific measurements like heart rate and pressure. Adding predictive routines and arbitrary values allows for situation-specific code we might not get elsewhere, whether it's estimating the finish time of a marathon or guessing just how much post-run beer is possible before the guilt sets in. On top of the new software platform, the 2.0 update brings a handful of major extensions from Suunto itself, including support for ANT+ and Foot POD sensors as well as an interval timer. The apps and upgrades help justify a relatively steep $500 price for the Ambit by turning it into a Swiss Army Knife for the wrist; when features are dictated more by imagination than a developer's whims, they might just save the cost of an early hardware replacement.