I've seen a few "SmartPort" SD card drive products pop up over the years, and each time I wondered what advantages they had over the venerable FloppyEMU. It's often a cost advantage, not a feature advantage. Most of the SmartPort SD card drives are just that — SmartPort-only, with no means of booting from a floppy disk image. The FloppyEMU costs more than the SmartPort hard disk only solutions, but you are basically paying for the ability to use it either as a SmartPort hard disk (with 4 drives to choose from), or floppy disk. The wDrive offered similar functionality, but as you may expect, the cost isn't that much cheaper than a FloppyEMU, and it appears to be unavailable these days too. (I personally think the FloppyEMU is more aesthetically pleasing than the wDrive, if such matters to you.)
For people like me who already own two FloppyEMU units (both with the acrylic cases on them), I've never been tempted to get a SmartPort-only solution because I already have that functionality. But for people who don't have the FloppyEMU or anything similar, deciding what to buy for an Apple II machine can be a bit challenging. It really boils down to what Apple II machine you have. In my case, my only Apple II is a IIc, so I tend to focus on those products.
If you too have a IIc and are considering a FloppyEMU so as to get floppy drive emulation, there is one important consideration. The internal floppy drive on an Apple IIc is the boot disk drive. Attach an external disk drive and put a disk in it and power on, and nothing will happen because you can't boot from external disk drives. At least, not unless you want to change that!
I have a ROM Xc which offers a "software" switch that will allow an externally attached floppy disk drive (real or FloppyEMU) to become the boot floppy drive. However, there are a few programs that don't play well with it, and those compatibility quirks ultimately led me to buy the BMOW Drive Switcher. The Drive Switcher is a hardware solution for the IIc. It sticks out on the back a little bit, but a tiny DIP switch lets you choose if you want the default behavior or if you want to make the externally attached FloppyEMU to be the boot drive. It works with all programs. No compatibility quirks.
If you have a FloppyEMU and an Apple IIc and no Drive Switcher, then you can only boot floppy disks from the IIc's internal floppy drive, but any bootable SmartPort volumes attached to the back port will be bootable whenever you don't have any floppy disk in the internal drive. For example, just leave a floppy out of the internal drive and put Total Replay on your SmartPort hard disk, and you can then boot from your Total Replay drive and enjoy all the games.
If you want something lower cost than the FloppyEMU and if you only care about SmartPort hard drive emulation (not floppies), then we can get back to the title of this thread by proclaiming that @Kay K.M.Mods has his new SPIISD kit out now which offers a FloppyEMU style experience with OLED screen and the PCB attached by ribbon cable:
en.infinityproducts.co.jp
It is only a SmartPort Hard Disk emulator and not a Floppy Disk Drive emulator, but if you are OK with that, it's a nice solution.
Kay's excellent blog article below explains how the SPIISD v1 (now v2) evolved out of the SmartPortSD open source project:
ameblo.jp
For people like me who already own two FloppyEMU units (both with the acrylic cases on them), I've never been tempted to get a SmartPort-only solution because I already have that functionality. But for people who don't have the FloppyEMU or anything similar, deciding what to buy for an Apple II machine can be a bit challenging. It really boils down to what Apple II machine you have. In my case, my only Apple II is a IIc, so I tend to focus on those products.
If you too have a IIc and are considering a FloppyEMU so as to get floppy drive emulation, there is one important consideration. The internal floppy drive on an Apple IIc is the boot disk drive. Attach an external disk drive and put a disk in it and power on, and nothing will happen because you can't boot from external disk drives. At least, not unless you want to change that!
If you have a FloppyEMU and an Apple IIc and no Drive Switcher, then you can only boot floppy disks from the IIc's internal floppy drive, but any bootable SmartPort volumes attached to the back port will be bootable whenever you don't have any floppy disk in the internal drive. For example, just leave a floppy out of the internal drive and put Total Replay on your SmartPort hard disk, and you can then boot from your Total Replay drive and enjoy all the games.
If you want something lower cost than the FloppyEMU and if you only care about SmartPort hard drive emulation (not floppies), then we can get back to the title of this thread by proclaiming that @Kay K.M.Mods has his new SPIISD kit out now which offers a FloppyEMU style experience with OLED screen and the PCB attached by ribbon cable:
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SPIISD V2 DIY KIT | infinityproducts
SPIISD: A High-Performance Smart Port Device for the Apple II Series The SPIISD is a high-performance smartport Hard Drive Emulator device designed for the Apple II series. With the release of version 2 (V2), the SPIISD now features a clear, easy-to-read OLED display, operated by simple...
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It is only a SmartPort Hard Disk emulator and not a Floppy Disk Drive emulator, but if you are OK with that, it's a nice solution.
Kay's excellent blog article below explains how the SPIISD v1 (now v2) evolved out of the SmartPortSD open source project:

『The SP2SD Project has begun!』
If you are not experienced with vintage computers and buy that Apple IIc or IIg…