They have really nice fetal monitors on ebay for reasonable costs. i also opted to get a 3D ultrasound . It cost me $160, but was very awesome to see the images other then my boyfriend thought the images were scary.
Mine was okay. Just depends on baby!
I just had a 3d/4d one at the beginning of this month at 27 Weeks def worth it!
I would say go for it :)) and as for the monitor its best to get a good one on eBay