When do you want these alerts?
If you are checking for crossovers using end-of-day data then setting up a scan with a software program like Metastock or Amibroker (and others), fed with EOD data from a provider like Premium Data, is a very simple and straightforward procedure.
If, on the other hand, you are wanting crossovers on live data (an intra-day crossover, maybe on hourly bars or whatever) then I know Metastock Pro (real-time), fed with live data like eSignal, will send you an email/SMS. There will be other software programs that will do this too, but Metastock is the one I am familiar with.
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Amibroker can send chart via email.
Never use it before, perhaps with a little programming.....
"AmiBroker allows you to define formula-based alerts. When alert is triggered a text can be displayed, user-defined sound played back, e-mail notification can be sent and any external application can be launched. This is all handled by single AlertIF function."
What type of trading are you doing? are you looking at buying stocks and holiding for long term, or day trading?
If you are day trading then i am not aware of any Crosses, that are profitable, otherwise id be using them.
If you want to long term invest on a cross, then EOD (end of day data) should be fine, as you won't miss much. But even then i woudlnt tade a position on a cross.
Have a look at some of the trading strategies and systems started by some of the more experienced traders and see what they do. Use the search tool and have a look. I think there are also some threads which show that crosses don't work. Good luck.