Hi Alex
If you download the open source uTasker project from the link below you can use it on the TWR-K70F120M, starting with a blinking LED.
Just select the define TWR_K70F120M for your board and the define BLINKEY to get the simple flashing LED. You can use almost any IDE to do this (KDS, CW, MCUXpresso, IAR, Keil, Rowley, etc.) and also run it in the Visual Studio as (real-time) K70 simulation.
Then you can simply add more features as you wish, once you get comfortable with things - e.g. remove BLINKEY and you will have also a command line interface on the UART, add USB_INTERFACE (and chose classes) and you have a working USB stack. Add ETH_INTERFACE and you have a TCP/IP stack with various services (web server, FTP, etc.), add SDCARD_SUPPORT and you have a complete FAT file system and you can then select many other peripheral operations (timers, communication interfaces) too.
Tutorial at http://www.utasker.com/docs/KINETIS/uTaskerV1.4_Kinetis.pdf
Various videos at https://www.youtube.com/watch?v=kWNlsAoMly4&list=PLWKlVb_MqDQFZAulrUywU30v869JBYi9Q
Support here or at http://www.utasker.com/forum/
If you move to other Kinetis parts just select the other board in config.h and the complete project moves to that board, so one can write applications and let then run on any board that has the required peripherals without porting requirements.
The project also includes various boot loaders and, using Visual Studio, you can simulate the chip (including Flash, interrupts, DMA, Ethernet, CAN, UARTs etc..) in order to learn all details in a simple and efficient manner. For later professional designs you can use it to work much faster and to more easily achieve reliable complete solutions.
Regards
Mark
http://www.utasker.com/kinetis.html
http://www.utasker.com/kinetis/TWR-K70F120M.html