If you have a signal that gives you, for example, a rising edge when engine starts,
and falling when it stops, should be easy using a Arduino Nano board (cheap) or an
ATTINY85 to output a select/trigger/address to your speech board.
Using mBlock to create program here is a start :
mBlock takes you block configuration and generates Arduino code from it, and then
programs the board.
mBlock will program Nano board using Arduino programmer utility, or use a Nano board
to program an 8 pin ATTINY85. Web shows examples of doing this.
Regards, Dana.