You can send anything in the GSM 7-bit alphabet, which has 128 characters rather than Base64's 64-entry index table.
They could gain a lot of efficiency by using a 127-entry index table (or 128 if the ESC character doesn't need to be avoided - I don't know how the Android SMS APIs handle it) rather than a 64-entry one.
They could gain a lot of efficiency by using a 127-entry index table (or 128 if the ESC character doesn't need to be avoided - I don't know how the Android SMS APIs handle it) rather than a 64-entry one.