The CHOMPI is a very fun project.. have considered building one myself over the years, but I think I have a bit more motivation to build a FundamentalFrequency LMN-3, which is in a similar form factor but is, imho, a bit more open ended with regards to what it can be used for ..

https://github.com/FundamentalFrequency

Either way the time has come for open source projects of this nature and form factor .. the world tires of overpriced junk from boutique vendors, and wants more DIY music making toys for the kids to rock out ..