For the M-PESA section of the mySafaricom app, users had to be redirected to the SIM Toolkit via a pop-up notification that would take a moment or two to pop up, asking for your M-PESA PIN to authenticate a transaction. This meant that you had to have your Safaricom SIM on a device to receive the aunthentication prompt and for you to enter the PIN.
But that is changing soon. Early adopters like Tech-ish have found out that the app now asks for your PIN from right within the app. This is possible currently when sending money, Lipa na M-Pesa, Withdrawals, under Bill manager, and when checking M-Pesa balance. The main takeaway of this move is that you can now have M-PESA work without necessarily having your SIM card with you. Of course, you will still need your Safaricom SIM Card when signing up to the app but after that, all you need is the app and access to the internet.