we didn't encounter any large electromagnetic fields and didn't set off any alarms that we know of (I had his card ready, just in case . . . we've had some issues with this at Target and
Walmart). And the rides were just fine, because he was under 42" and couldn't go on some of the ones with warnings, anyway. I would be a bit concerned about space mountain, being so close to an electromagnetic track (is that the right name?), but we won't have to worry about that for a few years.
WDW doesn't have any attractions that list electromaganetic interference problems. I think I remember they
used to, long ago (like 10-15 yrs ago).
I'm not sure what is different; whether they have electomagnetic fields that are shielded better or don't have any or feel that people with concerns about those would not be riding any of the attractions with warnings. I
do know that devices like pacemakers are shielded against interference better than they used to be. But, the best place to get information about that might be the manufacturer of your child's pacemaker.
If you go to the disABILITIES FAQs thread, post #3 in that thread does have a link to a past thread about magnetic fields.
I met with our cardiologist to go over which rides are safe for him. He could never ride one of the drop type rides or the high force roller coasters when he gets older. BUT - he can ride alot of things. I think it's important for everyone to speak directly with your doctor about what is safe for YOUR child.

All the rides with warnings are well marked. There is a warning icon on the park maps, on signs at the entrance to the queue and also before boarding. So, you don't have to worry that you will get on one by mistake.
Also in the disABILITIES FAQs thread, post # 3 has links to the Guidebook for Guests with Disabilities for each park. The Guidebook does give a list of attractions with warnings.
I'm glad to hear there aren't many pacer warnings. I did speak to our cardiologist and he said most things a 2 year old does are fine for him we don't really have to address limits at this point.
Most of the attractions that are OK for a 2 yr old are pretty tame.
The only things I can think of that might cause any questions would be:
-
Mickey's Barnstormer, which is a small version roller coaster
-
Tomorrowland Transit Authority, which is tame, but uses a magnetic induction motor. There is no warning listed for that attraction though.