I don't have any experience with email clients on the tablets, but as far as IM alerts I'm not sure exactly what you want. I think having the blue led flash is a stretch, since that is something rather specific to the tablet itself, and the majority of maemo applications are ports rather than things written for the tablet, some exceptions being things like Canola. Unfortunetly I'm pretty sure all of the IM clients are ports. Personally I use Pidgin for IM, and it doesn't flash, but it can play sounds rather loud, to the point I've never not heard them, you can change the sound, etc. Only time I've missed a message is when I've got the sound off and am tabbed to something other than the IM window.