get some incanal headphones. The cheaper ones are sometimes normal ear buds with squishy bits attached on to them, but the good ones are truly designed for the purpose of insertion into your ear. Drowns out about 30 decibels of outside noise, meaning you can hear someone talk, or a car engine as long as you're not blasting it. Doesn't slide out easily. Used by pro and amature race drivers so they can hear the pit crew better, but still hear what is going on around them.
No point in open air I think, you'd barely be able to hear them with the wind buffeting.
iPod zombies suck, yes, but we'll give you a fair warning (so does the packaging) about use around machinery. So pay attention, put it at a reasonable volume and ride safe.