I use an older Toshiba Portege' Tablet PC running win xp tablet. On it I run EAW SMAARt with a small m audio usb pre and audix tr40 as my test mic. I mainly stick with the tablet because one of the main consoles I use is the Avid Venue series which when hooked up to a router will allow control of the console via laptop and free software offered by avid. That combined with wireless control of my amps and processing, I have full control of the entire rig wirelessly. The tablet I use is larger than some out there, but for a couple hundred on ebay, it lets me control the entire rig and consoles, check email, browse the web etc. And if someone walks with it, its no large financial loss.
I very rarely do live recordings, but that tablet has been able to track 15 channels to nuendo with a pro fire 2626 on set without a problem, my ghetto cart setup haha. Generally if the band wants to record, we get a separate record rig and a 3 way splitter.
A friend of mine uses his macbook for Edwin Mccain. Running Max/MSP I believe where he has many different verbs and effects configured and then uses an IPAD via bluetooth to control it/tap tempos/mutes etc... That way he can put the IPAD on the console and keep the macbook out of sight and away from the dangers of drunk people. He keeps his ipad with him when he leaves the console. It seems to work pretty well for him.
As far as different apps, I use programs offered by manufactures of the gear I use, Then I use smaart for time alignment of the rig and then once the show is going the I put the display to rta and coherence graphs. I also have an fft program on my iphone called FFT by studio Six, also on the phone is an inclinometer and spl meter.
I know waves makes a live rack to put in waves plugins, but I have never used it.
Ill get you a specific model of the tablet once I get back to where it is.