How about making necessary contition - to send a message everyday? It'll make tontine harder and profitable.
And is it possible to make a program, that will automatize this participant-verification-process and, in fact, give a huge advantage to it's inventor? Can someone cheat your system in that way?
Logging in every day would be a pain in the butt.
I think logging in once a month and using biometric identification would be a good start to prevent cheating