Mark over at www.brainwagon.org has posted some interesting info about sending hellschreiber from an Arduino (see Marks image above). He has used KD1JVs oscillator circuit that was originally used for the wireless morse code thermometer project. Mark has written code for the Atmel Tiny 13A uC for Hellschreiber transmission. You can find code on his website. Below you can study the schematic designed by KD1JV ( you can find more info over at KD1JVs site http://kd1jv.qrpradio.com/temp2morse/temp2morse.htm).
The way this circuit works is that the XTAL oscillator (left) is powered on and off via PB3 output from the Atmel uC. The emitter of the 2N3904 has been tapped with a 6” antenna. Here a DS18B20 Maxim temp chip is used for accurate temp sensing. The temp is sent out via Hellschreiber together with the callsign. The circuit could be expanded with a buffer tapping the signal from the emitter of Q1. That buffer could feed a power amplifier (well filtered of course). Then a Hellschreiber telemetry beacon could be set up. Cool idea!