PBA
I asked the asktherabbi (gateways) if it is muter to text during Shacharis and this was his answer:
Personally, during Shacharis I think that it is forbidden at all points in davening because it is a cause of hesech haDa’as. At the very least I do not see how it can considered to be less than talking and it should be forbidden for all the moments that talking is forbidden.