Unlike the iDM11 (or the Jambox), this model doesn't have a built-in microphone for speakerphone calls, but it does have a rechargeable battery. You charge the speaker via a cable that also doubles as an audio connection for non-Bluetooth devices. iHome calls this a 2-in-1 USB/3.5mm audio to micro USB cable. You basically plug the 3.5mm jack that's part of the cable into the headphone jack or auxiliary input on the device to output sound to the speaker. It works well enough, but if you lose the cable, you're out of luck.
The iDM8 and iDM11 sound pretty similar, though the iDM11 arguably offers slightly better sound. Neither speaker is going to blow you away, but they're decent enough considering their small size and relatively affordable price tags (the iDM8 list for $60 while the iDM11 goes for $70).
In many ways the iDM8 is on par with, which costs a little more but has speakerphone capabilities like the iDM11.
Overall, I came away liking the iDM8 and think it's a pretty good little portable Bluetooth speaker for the money. However, as I said in my review of the iDM11, I'm a little more partial to that model and think it's worth spending the extra $10 on it.
That said, if you're smitten with the bulbous the design of the iDM8 and don't mind the missing speakerphone option, I have no problem recommending it.