Cron already supports sending email for jobs (or at least the cron's on Unix/Linux machines do so). Just don't redirect the output anywhere and cron emails it to the owner of the cron job. Assuming that MacOS's cron is not too far modified, all you need is a replacement "sendmail" command, in the location that MacOS cron would look for it, that submits cron's output to an SMTP server for delivery.

Given that MacOS already ships with Tcl/Tk, if you install TclLib (http://wiki.tcl.tk/1246) such that the native Tcl/Tk can find it (note, I have no Mac, so I have no knowledge of 'how' to install TclLib on MacOS) then you need a four line Tcl script to create a replacement "sendmail" command:

    #!/usr/bin/tclsh

    package require mime
    package require smtp

    set mesg [::mime::initialize -string [read stdin]]

    ::smtp::sendmessage $mesg -servers smtp.server.name.com \
        -client this.machines.name.com \
        -originator email@address.to.use.as.from.com \
        -recipients destination@email.address.com

Replace 'smtp.server.name.com', 'this.machines.name.com', 'email@address.to.use.as.from.com', and 'destination@email.address.com' with the appropriate items for your environment and you (on Linux, at least) will be good to go. Hopefully MacOS's cron is not too far afield from standard Unix cron.