Benefits of handheld computers   Jerry Garfunkel
Some of the benefits of Handheld computer (HH) activity in the classroom include the following: 
Projects are wonderful learning activities.  The HHs facilitate project oriented constructivist learning because it gives each student his/her own mobile computer as a personal aide. 
The features of HHs as far as educational tools go, are not that unique from small PCs (i.e. Sony Vaio).  Both are "small" computers;  both are communication devices,  both are portable (to different degrees).  Applications such as streaming audio/video, data gathering/processing/reporting, can be done in both environments.  Transaction processing takes on a new dimension in the HH community not (usually) associated with PCs.  Transaction processing between HHs is more like "process control" applications where computers control machine behavior, based on real-time input factors.  Only in this case the "machine" in question is another HH.  These transactions are the "HI" (highly interactive) in Dr. Elliott Soloway's HI-CE. Certainly a unique feature of the HHs is their cost.  This important factor will make the experiments now underway to produce high valued educational products (HI-CE, Concord, etc.) successfully integrate with our current curricula, naturally. The educational value ("bang-for-the-buck") will be demonstrably too great to resist.  I don't know precisely how one would measure the size of this "bang."   That is why I described it as "demonstrably too great to resist."  This "bang" is another illustration of the "threshold" theory, described elsewhere. We will know when we are there. We just may not know exactly when we arrived.
So what are the significant differences that suggest how one might exploit the HHs?  First (and formost?) is the different degrees to which these computers (laptops and HHs) are portable.  Clearly HHs can be used in places and in ways we might never have considered.  It is not just portable; it is "extremely portable."  This in itself however is not enough of an argument to intergrate HHs into all curricula.  It is the combination of its "extreme portability" with each of the other features that gives the HH its uniqueness.  For a long time we've been able to gather and process data, but now we can do it at the source of the data much more easily because of the HH's "expreme portability."  We have been communicating via voice and video (and text, IM) for some time; but now, because of its extreme portability, we can do it at the place and at the moment of the activity.  We've been able to communicate in a classroom network (school-wide, district-wide, world-wide)  with other members of our network, but now we can create networks and exploit their collaborative potential, in places we would not (could not?) have considered before, because of the HH's extreme portability.  This extreme portability includes unique capabilities not available on a small PC.  Even a small  PC (usually) requires "set up." This set up may be nothing more than setting it down and turning it on, but it is not meant to be ubiquitous in the students other activities.  HHs on the other hand  power on/off,  beam to each other,  stream video in/out and collect data - all while students are on the move. "Finger buttons" enable these features. The HHs in this scenario are truly ubiquitous. They are more than computers at this point they become "smart tools." 
Just like a generic remote control unit one can buy at a Radio Shack (or one of the  new ultra-programmable units),  a smart tool can be programmed to BE whatever the student wants it to BE in any given activity. 
These benefits of HHs allow us to build, more easily, collaborative projects and  multi-discipline projects.  These projects can (should) be outside of the classroom.  Like all learning tools, these tools should be tailored to the specific intelligences of each student.  That is, each student may exploit a different benefit of the HHs.  All of this takes careful up-front planning.
The greatest barrier to the intergration of HHs into our schools is the resistance to technology exhibited by many schools' faculties.  Although this is changing as a new generation of teachers and supervisors takes control of the schools, there always is  tension between an older administration and a younger one.  Technology is always advancing. Other barriers are money.  While HHs are much cheaper than PCs they still represent a line item in the budget and often they are in addition to PCs not instead of PC. Faculty needs to be trained.  Clever in-service staff development  programs must be implemented.  The more technology-oriented faculty should be used more in a mentoring role to speed up the integration of HHs in to the curricula  of all subjects and in all grades.