we are currently in process of updating the list and will be out soon. For suggestion you can create a new suggestion topic in the community and we will look into it.
For accelerometer to send a tuple here is the code:
x = mpu6050.getAccX();
y = mpu6050.getAccY();
z = mpu6050.getAccZ();
char buffer[50];
buffer[0] = '[';
size_t offset = 1;
dtostrf(x, 1, 3, &buffer[offset]);
offset += strlen(&buffer[offset]);
buffer[offset++] = ',';
dtostrf(y, 1, 3, &buffer[offset]);
offset += strlen(&buffer[offset]);
buffer[offset++] = ',';
dtostrf(z, 1, 3, &buffer[offset]);
offset += strlen(&buffer[offset]);
buffer[offset++] = ']';
buffer[offset] = 0;
Serial.println(buffer);
Cayenne.virtualWrite(1, buffer, "accel", "g");