Actually, I forgot about a chip I used a few years ago, PCF2129A, from NXP. 0.65uA, +/-3PPM with INTERNAL TXCO, 20pin SOIC, either SPI or I2C interface and lots of interrupt choices.
I forgot because its too big for most of my applications now, but it is a very nice chip... Did I mention +/-3PPM with INTERNAL oscillator - no xtal needed.
Tom