At the time of writing [October 2015], there is limited instructions from Texas Instruments on how to build your own DevPack for the CC2650 SensorTag. These notes have been derived from studying the Build Your Own DevPack "Guide" and SensorTag / example DevPack schematics.
The CC2650 Sensor Tag includes a 20 pin Samtec connector, Part No LSS-110-01-F-DV-A for spinning your own DevPacks. The connector is self mating, hence you don't need to worry about male and female versions.
Very few of the electronics catalog companies (Element 14, RS-Components, Digikey, Mouser) stock this part, and thus you may need to acquire the connector directly from Samtec
The following table details the SensorTag DevPack Expansion connector:
Texas Instruments appear to have multiple product pages for the Sensor Tag DevPacks, some with schematics and some without. This makes finding the schematics and design files for DEVPACK-DEBUG, DEVPACK-WATCH and DEVPACK_LED_AUDIO files difficult if you land on the wrong page.
Below is a list of direct links: