Is there an app that I can use to communicate to our employees through text messaging?

There is a way to string together an email address based on each person's phone # -- then leveraging the native email notifications to send texts. However you must know EVERY persons cell provider to be able to create the email address. For example something like [phone number]&att.net -- the "att.net" you'd have to store as part of the person's record in QB to concatenate that to the phone #. If this is possible, check this out: 


var text phoneone = Right ([Cell Phone], 13);
var text phonetwo = Left ($phoneone, 3);
var text phonethree = Mid ($phoneone, 6, 3);
var text phonefour = Right ($phoneone, 4);
var text phonefive = $phonetwo & $phonethree & $phonefour;
var text email = If([Carrier]="AT&T","@txt.att.net",[Carrier]="Verizon", "@vtext.com", [Carrier]="Sprint", "@messaging.sprintpcs.com", [Carrier]="T-Mobile", "@tmomail.net", [Carrier]="MetroPCS", "@mymetropcs.com", "");
var text conct = $phonefive & $email;
$conct

If the above isn't achievable then a simple integration between QB and Workato or Zapier with Twilio or their internal SMS (depends on volume/cost) could be done easily.