As much as I like Blynk... I don't see any benefit (aside from the technical challenge) of utilising it for this one way transmission of limited data and limited frequency.
Since Blynk really requires a server link to transmit any data. You would sacrifice programming effort, cell data charges (for the extra data overhead) and possibly a bit extra battery power just to make that all work reliably, all for a twice daily check in, when a simple SMS will do the same thing.
That all said... there is that whole challenge thing that sometimes makes the success worth the little extra effort and expense. Make the traps with exercise wheels powering little generators and lots of Blynk controlled wheel speed, rat respiration rates, etc... oh and RGB lighting and buzzers to entertain the App user and the rat...
...at least until the huntsman comes and thunks it (the rat, not the user) on the head