In the release notes for Firmware v6.0 for the Tesla Model S, there's mention of the ability to start the Model S with an iPhone app and (in a few weeks) an Android app.
This means that Model S owners won't need a keyfob to start their electric sedans.
Firmware 6.0 Will Allow One To Start A Model S Without The Key Fob
Firmware 6.0 is reportedly rolling out now, so iPhone users will get this app-starting ability just as soon as their Model S gets this latest updated. Android users have "a few weeks" to wait before their phone will bring to life the Model S.
Additionally, Firmware 6.0 brings with it a new power management setting "Nightly," which switches the Model S to energy-saving mode from 10 PM to 5 AM. Other changes for Firmware 6.0 seem relatively minor:
Firmware 6.0 Highlights
Source: 9to5 Mac