I don't remember if it does the auto-SMS, but Llama (FOSS, on the Play Store) can certainly use the calendar plus a whole bunch of other conditions to silence the phone, change "profiles" (enabling things like different ringtones at home and work, or silencing/changing some notification with the LlamaTones ringtone selector) and generally trigger actions.
My phones: Galaxy Note II SGH-T889V (with LTE enabled
/ ext4 SD card support on TouchWiz ROMs
), Motorola XT-1045 Moto G LTE (TWRP
Previous phones: Nexus S GT-I9020A, Galaxy Gio GT-S5660M (Arpeggiomod ROM
/ Discussion, stock rooted ROM
), Motorola XT-1032 Moto G.
Phones for which I play "tech support" for family and friends: Galaxy Nexus GT-I9250, Galaxy Q SGH-T589R, Galaxy 551 GT-I5510M, LG C-800G Eclypse, Motorola XT-1032 Moto G