thanks ! mumbles looks very good on the first view ... i found a tutorial
to install it on the raspberry ... it sounds a little bit tricky (special network configuration with the router - but nothing more) and possible - it looks, that mumbles is a good solution!
maybe somebody here tried this and can say anything about the usability? it should run full day and if somebody call me i have only to use the headphones .- without running big pc or other technic