Here is the schematic of the IQ Keyer Project. You can customize the keyer for you specific application by eliminating portions of the circuitry.
Examples:
If you want to run the keyer from USB power only remove VIN, U3 and the associated components
if you don't have an baseband IQ SDR and you want to use the keyer with a conventional transceiver remove U2, RLY1,T1 and T2 and all of those caps and resistors
HobbyPCB makes a complete kit which includes everything on this schematic, PCB (with SMT components installed), enclosure and an Arduino Nano.
There is also the possibility of adding things to the IQ Keyer for even more features for example:
More memory buttons connected then to the MEM jack
An RCA jack on the ST-KEY jack to add a tune/straight key