If your goal is to make sure they call you, before they don't come (because if they don't want to work, they don't want to work, let's not fool ourselves by pretending there's a reliable fix to that), you have to make it clear on day 1:

"If you decide to not come to work, for whatever reason, legit or otherwise... Just call me so I know you won't come and I can organize differently, leave me a message, sms, whatever you prefer, but do it, tell me "I won't come tomorrow", no question asked , just don't be an ass by not letting me know in advance, and if you don't know when you'll be able to come back, just warn me in advance every time you know you'll miss a day. Of course, the day you come back, you'll need to give me a valid justification for your absence; a doctor's note for instance, or any other valid administrative proof to justify your absence. If you don't, well... There will be consequences of course."

Something along those lines, implying that they can "not show up", it's ok, but what's not, is to let you down by not warning you.

...

Now of course they can cheat, come up with made up stuffs, but that's beside the point, they can do it anyways, where there's a will there's a way. But at least you can ensure you don't end up caught off guard for your work's daily schedule. And when they come back, either with a valid or not so valid excuse... It's not a drama, no big deal... As long as they've warned you in advance as we all agreed on day1... Because if they did not, that's when you put them in the hot seat, that's not okay like not at all, no more mister nice guy you've been warned, it's betrayal, breach of trust, and that's a big deal "because you're supposed to be a grown man"

OMG! Somebody is being agreeable in this thread. Must call the Internet Police. This behavior must be contained!