Open hardware that supports ASK/FSK transmit on 315/433MHz ISM bands. General point is to spoof TPMS sensors but it could be used for any type of ASK/FSK transmittion on bands supported by the IC.
Big thanks to rtl_433 project, wouldn't exist without their hard work for decoding the TPMS in the first place.
Boards are for sale https://www.tindie.com/products/gcormier/tpms-silencer/