Have been working on an OSD compatible with MinimOSD, but based on a STM32F4. The OSD can do vector graphics and also can send data to the ground station using the unused frames after the Vsync pulses ( like teletext).( I use this to send data to my antenna tracker.) The OSD is desigtned to be a drop in replacement for MinimOSD and accepts Mavlink data. Also has 2 audio channels ( so can be used e.g fo vario) and various peripherals ( serial port, i2C, SPI and PWM capture etc,) broken out on headers.
Here is a video of the prototype working