Five years ago, I was looking for a way to initiate calls from a hosted WebDirect solution. I searched the web and found an approach that worked: embedding the text, "tel: [phone#]" in a WebViewer, where [phone#] refers to a phone field.
There was a thing that I initially experienced as a bug: when calling a land line, I got the expected behavior of a dialog with the option to place a call, but when calling a mobile number, it brought up a dialog that would let you choose from among options (call, text, facetime, etc.). I quickly saw that this bug was actually something of a feature, in that texting was an option, too!
Now, however, while that option is available still on Android, apparently, it isn't on iPhone. I tried making a separate button for texting, and replacing "tel"in that WebViewer with what I thought would be obvious contenders for the job, like "txt" and "sms". That did not work.
I do think that having separate buttons (and exclusive dialogs) for calling and texting would be better. Any suggestions on how to accomplish this, in particular the texting option? That is, the user clicks on a text icon, and they initiate a text message to that number (but obviously do not yet send it). Alternatively, if that isn't possible, making the old way work again on iPhones (i.e. click on phone icon and if mobile one gets the choice of phone, text, etc.)
My preference is for a solution within FileMaker itself, if possible.