DTMFsynth is a free simple DTMF synthesiser intended for electronics hobbyists and amateur radio operators.
It has been tested with DTMF decoder chips and telephony.
This App doesn’t have any phone number memory, but could be used to navigate phone menus.
There is an option in settings to turn the screen upside down to bring the iPhone speaker to the top.
No pre-recorded DTMF samples are used. All DTMF is generated in low level audio library.
For iDevices with larger screens, pressing the time display will output the current time with DTMF tones.
Format is HH:MM:SS:CC where CC is centiseconds, and is always rounded down to zero.