So, you have two sockets on the MMX's... one for the extension box and the other for illuminated swingers.
Do you know what type of signal is sent to the extension box? Is it a signal that replicates the function of the alarm, i.e. beeps/lights up on a run, then latches for 20 secs etc. or does the extension box do something else?
The power-out socket
appears to be a piggy-back function of the original LED's, purely for illuminated swingers.
Do you wish to monitor the alarms - wired, or wirelessly?
If wirelessly:
How do you intend to power each wireless transmitter attached to an alarm?
How will you differentiate between multiple alarms of your own, and how will you negate any possibility of causing interference to other anglers using wireless systems?
I'll admit that I'm a bit of a tackle-tart and have the Delkim TXi Plus's with a 6ch receiver.
They work. And in a far superior capacity than anything I could design.
I don't want to stifle innovation or dampen your spirits of making something workable for yourself, but as you know, there are already solutions out there on the market, probably made in China or somewhere else with cheap labour, that will be a complete package for less money than you could source the individual components for.
Carping over here
is big business, but unless you come up with something
totally new that blows the competition out of the water, so to speak, you'll just be offering another vanilla product of which there are many already established models available.
A little something to think about... I hope you can prove me wrong though.