I'm looking for software to help manage and communicate with our caregivers.

Thank you, all. These answers were very helpful.

You might also consider using the "hand off" method when hospital shifts change. End of shift workers identify issues that need to be followed up on by the incoming shift. These should obviously be noted in the handbook notes.

monteros, are you using caregivers via a professional Agency, or are the caregivers independent contractors?

Veronica, above, had a lot of good ideas.

I used an Agency that was licensed, bonded, insured, and had workman's comp in case anyone got hurt on the job. The caregivers are to call in to the main office when they arrive at the house, using the client's telephone. When the 1st shift was over, she/he waited until the 2nd shift arrived and then they gave that person any information that was needed.

There was also a notebook, provided by the Agency, to put down what my Dad had eaten, if he had a shower, how Dad was feeling, if the caregiver washed the sheets/towels, etc.

I had a contract with the Agency that spelled out what is required from the caregivers, and anything special. Because of that, I didn't bother the caregivers, I let them do their work. Dad had zero complaints so I knew all was well. Also what was great, if a regularly scheduled caregiver couldn't come, then the Agency would assign another caregiver. The main office would let me know. Plus the main office would scan to me a weekly copy of the names of the caregivers, what days, and what shifts.

As for software, I wouldn't bother with that. Not everyone is techie. One of my Dad's favorite caregivers still used a flip phone. And so do I.

Mostly in the case of home caregivers they keep a book in the house and each shift writes a report. Software is a nice idea but some will find it difficult to learn and if you are employing CNAs they are unlikely to be very experienced.
You can post a list of everyones phone (probably cell) so they can easily talk. Any problems should be immediately reported to you.
This may be a nuisance but have each call you when they arrive and leave. they should also enter this in the notebook.
Make a habit of calling regularly and stop in unexpectedly especially at night when you may catch them sleeping.
Establish rules before they start and give each a list of duties plus post one in the house. The fridge is a good place. Decide whether you will provide snacks or require them to bring their own.
If Dad is a DNR post a copy on the fridge and on the back of the front door.

I know this is not what you asked and you are trying to work out an efficient way of managing paid caregivers.

Basically there isn't one due to the nature of the job. This is an entry level healthcare job and requires minimal training to be licensed. There is usually a lot going on in their lives and they get exhausted. Private duty is a lot easier than working in a nursing home or hospital and is kinder on older bodies. That is not to say you won't get wonderful caring individuals to take care of your father but just be vigilant.