Buy and sell signal with quantmod?

HI there,

I'm using quantmod to display my finance data with chartSeries(). I  
already calculated the buy and sell indicators in the R code, but it  
would be nice if I could display a sell and buy symbol (like an  
arrowhead or a bigger dot with different colors) in the chart. Is this  
possible to do that with quantmod or is there a better solution for my  
problem?

My actual project is to port the whole trading system from  
TradersStudio to R, so I can optimize the algorithmus behind. And  
TradersStudio shows you the indicators where you should buy and sell...

I'm sorry for all the newbie questions, but I'm still a student ;)

Thank you, Michael